[mdns] Renamed mDNS abstract layer to DNS-SD (#10381)

Abstract layer providing DNS Service Discovery functionalities
is currently called mDNS, but mDNS is actually a DNS-SD specific
implementation. Abstract layer should be named DNS-SD, while
mDNS and SRP should be modules implementing DNS-SD API.

Overall 1:1 changes from mDNS naming to dnssd, including:
* src/lib/mdns -> src/lib/dnssd
* lib/mdns/minimal -> lib/dnssd/minimal_mdns
* app/server/Mdns -> app/server/Dnssd
* MdnsImpl -> DnssdImpl
* Mdns namespace -> Dnssd namespace
diff --git a/src/controller/BUILD.gn b/src/controller/BUILD.gn
index cc80ba8..9616fb7 100644
--- a/src/controller/BUILD.gn
+++ b/src/controller/BUILD.gn
@@ -25,7 +25,7 @@
   output_name = "libChipController"
 
   sources = [
-    "AbstractMdnsDiscoveryController.cpp",
+    "AbstractDnssdDiscoveryController.cpp",
     "CHIPCluster.cpp",
     "CHIPCluster.h",
     "CHIPCommissionableNodeController.cpp",
@@ -51,7 +51,7 @@
     "${chip_root}/src/app",
     "${chip_root}/src/app/util:device_callbacks_manager",
     "${chip_root}/src/lib/core",
-    "${chip_root}/src/lib/mdns",
+    "${chip_root}/src/lib/dnssd",
     "${chip_root}/src/lib/support",
     "${chip_root}/src/messaging",
     "${chip_root}/src/platform",