Add register_{execution_platforms,toolchains} directives to MODULE.ba…

…zel files

These are intended to replace the {execution_platforms,toolchains}_to_register attribtues on the module() directive, which are a bit harder to use since they have to be grouped up together near the top.

bazelbuild#15829

RELNOTES: Added new register_{execution_platforms,toolchains} directives to the MODULE.bazel file, to replace the {execution_platforms,toolchains}_to_register attributes on the module() directive.
PiperOrigin-RevId: 459714400
Change-Id: If8a25ef92ac695a3f012d54d0e189d8ae25d0833

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Module.java

@@ -21,6 +21,7 @@
 import com.google.common.collect.Maps;
 import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.util.Map;
 import java.util.function.UnaryOperator;
 import javax.annotation.Nullable;