toolchain: Support Kconfig-based C++ version selection Enables automatic selection of the C++ standard flag (-std=c++XX) based on the CONFIG_STD_CPP* Kconfig choice. Supported versions: 98, 11, 14, 17, 20, 23. Implemented by defining generic c++XX features in toolchain/args/BUILD.bazel and using select on Kconfig in all toolchains (including native_sim). TAG=agy CONV=66f377df-07e2-4b31-b652-bc93477153b4 Change-Id: I45fac3db579422c53880b1a9b0575baa1793651b Reviewed-on: https://pigweed-review.googlesource.com/c/zephyr/zephyr-bazel/+/438113 (cherry picked from commit 8074162f73105af00ba894e1f6a8fd96ca7399a0) Reviewed-on: https://pigweed-review.googlesource.com/c/zephyr/zephyr-bazel/+/440234