pw_toolchain: Add back support for adding sanitizers to host toolchains
pw_toolchain: Add back support for adding sanitizers to host toolchains

The pw_toolchain_SANITIZERS arg was moved to only affect the fuzzer
toolchain, but it is useful across all toolchains that don't already
have sanitizers specified. Add back to debug, size, speed host_clang
toolchains.

Test: gn gen out --args='pw_toolchain_SANITIZERS=["address"]'
  Check compile_commands for -fsanitize=address

Change-Id: If35c26e58c4ea39557bf1071b3df28de3881d981
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/68282
Commit-Queue: Austin Foxley <1af965fecf930e25ddc640dc59fb3dfab8e1466a@google.com>
Reviewed-by: Ted Pudlik <c7372cc3e451acc046049fca9e050bcb2a4a3d11@google.com>
Reviewed-by: Ali Zhang <101974175ff73f104389b21e58229a7713cff21f@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed