[roll] Roll fuchsia [bazel][idk] Allow select() for idk_cc_source_library() files

Previously, the `hdrs` and `srcs` attributes of
`idk_cc_source_library()` were not configurable and other attributes had
to be used for Fuchsia-only and non-Fuchsia files. This change makes
`hdrs` and `srcs` configurable and removes those other attributes.
Callers can now use any valid `select()` statement to conditionally
specify source files.

Use a rule in `idk_cc_source_library()` to perform operations on the
attributes and expose the results in a provider that is then passed in a
new `idk_atom()` attribute. `idk_atom()` now has two mechanisms for
specifying some values, allowing most atom types to continue using the
simpler attributes rather than defining a rule to populate the provider.

Update bazel2gn to support `select()` statements in
`hdrs_for_internal_use` and to delete support for the removed
attributes.

`[non_]fuchsia_deps` will be addressed separately.

NO_IFTTT=Changed a variable used for `FuchsiaIdkAtomInfo`; changes to `_idk_cc_source_library()` and //zircon/system/ulib/zx/BUILD.bazel are Bazel-specific.

Original-Bug: 417305295
Test: fx bazel build --config=fuchsia --copt="-ffuchsia-api-level=4293918720" //build/bazel/bazel_idk/tests:build_only_tests
Test: fx test --host bazel2gn_tests
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1538402
Original-Revision: c775540be6a941e77ae7196be9ade20065634231
GitOrigin-RevId: 39e78b8de2980e01dd6959c28ed1f27fd45b76c9
Change-Id: I6b4e918161385b09040a54976bc617768146f962