Remove unused pw_board_led module

Removes all references to pw_board_led which is part of the
experimental repo:
https://pigweed.googlesource.com/pigweed/experimental/+/refs/heads/main/

Change-Id: I0d124a0518efd71da7d0b638c53605b67ccb96c4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/201050
Pigweed-Auto-Submit: Anthony DiGirolamo <tonymd@google.com>
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed-service-accounts.iam.gserviceaccount.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
diff --git a/applications/32blit_demo/BUILD.gn b/applications/32blit_demo/BUILD.gn
index 842e161..3cf7a39 100644
--- a/applications/32blit_demo/BUILD.gn
+++ b/applications/32blit_demo/BUILD.gn
@@ -26,7 +26,6 @@
 pw_executable("32blit_demo") {
   sources = [ "main.cc" ]
   deps = [
-    "$dir_pw_board_led",
     "$dir_pw_color",
     "$dir_pw_display",
     "$dir_pw_draw",
diff --git a/applications/32blit_demo/main.cc b/applications/32blit_demo/main.cc
index 63be86c..078f5db 100644
--- a/applications/32blit_demo/main.cc
+++ b/applications/32blit_demo/main.cc
@@ -22,7 +22,6 @@
 #include "libkudzu/random.h"
 #include "pw_assert/assert.h"
 #include "pw_assert/check.h"
-#include "pw_board_led/led.h"
 #include "pw_color/color.h"
 #include "pw_color/colors_endesga32.h"
 #include "pw_color/colors_pico8.h"
@@ -112,7 +111,6 @@
   // Timing variables
   kudzu::FrameCounter frame_counter = kudzu::FrameCounter();
 
-  pw::board_led::Init();
   PW_CHECK_OK(Common::Init());
 
   Display& display = Common::GetDisplay();
diff --git a/applications/badge/BUILD.gn b/applications/badge/BUILD.gn
index 3623d6b..02eac7b 100644
--- a/applications/badge/BUILD.gn
+++ b/applications/badge/BUILD.gn
@@ -34,7 +34,6 @@
     "pw_logo5x7.h",
   ]
   deps = [
-    "$dir_pw_board_led",
     "$dir_pw_color",
     "$dir_pw_display",
     "$dir_pw_draw",
diff --git a/applications/badge/main.cc b/applications/badge/main.cc
index e4b288b..cf7cc99 100644
--- a/applications/badge/main.cc
+++ b/applications/badge/main.cc
@@ -30,7 +30,6 @@
 #include "pw_assert/assert.h"
 #include "pw_assert/check.h"
 #include "pw_banner46x10.h"
-#include "pw_board_led/led.h"
 #include "pw_color/color.h"
 #include "pw_color/colors_endesga32.h"
 #include "pw_color/colors_pico8.h"
@@ -234,7 +233,6 @@
 void MainTask(void*) {
   kudzu::FrameCounter frame_counter = kudzu::FrameCounter();
 
-  pw::board_led::Init();
   PW_CHECK_OK(Common::Init());
 
   Display& display = Common::GetDisplay();
diff --git a/applications/snake/BUILD.gn b/applications/snake/BUILD.gn
index ed14b1a..4e79b69 100644
--- a/applications/snake/BUILD.gn
+++ b/applications/snake/BUILD.gn
@@ -66,7 +66,6 @@
   sources = [ "main.cc" ]
   deps = [
     ":game",
-    "$dir_pw_board_led",
     "$dir_pw_chrono:system_clock",
     "$dir_pw_display",
     "$dir_pw_framebuffer",
diff --git a/applications/snake/main.cc b/applications/snake/main.cc
index d7a9f86..d49ce6e 100644
--- a/applications/snake/main.cc
+++ b/applications/snake/main.cc
@@ -20,7 +20,6 @@
 #include "graphics/surface.hpp"
 #include "libkudzu/framecounter.h"
 #include "pw_assert/check.h"
-#include "pw_board_led/led.h"
 #include "pw_display/display.h"
 #include "pw_framebuffer/framebuffer.h"
 #include "pw_log/log.h"
@@ -57,7 +56,6 @@
 };
 
 void MainTask(void*) {
-  pw::board_led::Init();
   PW_CHECK_OK(Common::Init());
 
   pw::display::Display& display = Common::GetDisplay();
diff --git a/applications/terminal_display/BUILD.gn b/applications/terminal_display/BUILD.gn
index 3b52fe0..21dc019 100644
--- a/applications/terminal_display/BUILD.gn
+++ b/applications/terminal_display/BUILD.gn
@@ -38,7 +38,6 @@
   sources = [ "main.cc" ]
   deps = [
     ":text_buffer",
-    "$dir_pw_board_led",
     "$dir_pw_color",
     "$dir_pw_containers:vector",
     "$dir_pw_display",
diff --git a/applications/terminal_display/main.cc b/applications/terminal_display/main.cc
index 8d6818a..9480f48 100644
--- a/applications/terminal_display/main.cc
+++ b/applications/terminal_display/main.cc
@@ -26,7 +26,6 @@
 #include "libkudzu/framecounter.h"
 #include "pw_assert/assert.h"
 #include "pw_assert/check.h"
-#include "pw_board_led/led.h"
 #include "pw_color/color.h"
 #include "pw_color/colors_endesga32.h"
 #include "pw_color/colors_pico8.h"
@@ -392,7 +391,6 @@
   // TODO(tonymd): Is there a way to hook this up outside of log_basic?
   // pw::log_basic::SetOutput(LogCallback);
 
-  pw::board_led::Init();
   PW_CHECK_OK(Common::Init());
 
   Display& display = Common::GetDisplay();
diff --git a/targets/host/BUILD.gn b/targets/host/BUILD.gn
index 15e4e3a..fa69b2c 100644
--- a/targets/host/BUILD.gn
+++ b/targets/host/BUILD.gn
@@ -43,8 +43,5 @@
     if (dir_pw_third_party_imgui != "") {
       app_common_BACKEND = "//applications/app_common_impl:host_imgui"
     }
-
-    pw_board_led_BACKEND = dir_pw_board_led_host
-    pw_spin_delay_BACKEND = dir_pw_spin_delay_host
   }
 }
diff --git a/targets/rp2040/BUILD.gn b/targets/rp2040/BUILD.gn
index ae3ba35..806989d 100644
--- a/targets/rp2040/BUILD.gn
+++ b/targets/rp2040/BUILD.gn
@@ -73,10 +73,9 @@
     pw_sync_COUNTING_SEMAPHORE_BACKEND =
         "$dir_pw_sync_freertos:counting_semaphore"
 
-    # Configure backend for pw_board_led
-    pw_board_led_BACKEND = "$dir_pw_board_led_pico"
-
     # Configure backend for pw_spin_delay
+    # This is still used by pw_display_driver_st7789/display_driver.cc:
+    # https://pigweed.googlesource.com/pigweed/experimental/+/refs/heads/main/pw_display_driver_st7789/display_driver.cc#115
     pw_spin_delay_BACKEND = "$dir_pw_spin_delay_rp2040"
 
     app_common_BACKEND = "//applications/app_common_impl:pico_st7789_pio"