Remove unused ObjcCommandLine flags

[dabanki]

These flags have been identified as obsolete. We are removing their references from Bazel as precursor work towards Starlarkifying Apple related flags, eventually removing the fragment all together.

See bazelbuild/rules_apple#2845.

[gregestren]

What was the story on removing this?

[dabanki]

There's still some references internally - and this function itself should be converted to starlark and replace the usages. I wanted to handle that in a separate task, but once it's not referenced anymore it should be fine to delete!

[dabanki]

cc @keith, @brentleyjones

[keith]

LGTM, notes:

• experimental_objc_fastbuild_options - i've been trying to remove this one for a while Remove --experimental_objc_fastbuild_options #27504
• ios_signing_cert_name / signing_certificate_name - this one is currently used in rules_apple but looks like it could probably be removed
• objc_debug_with_GLIBCXX - I don't think this was ever really used, but it just adds some -D flags so either way i think it's fine
• incompatible_avoid_hardcoded_objc_compilation_flags - i just recently flipped this 3b67b87, it's in 9.x so should be fine to remove @ HEAD
• incompatible_disable_native_apple_binary_rule - was a no-op