Add `module_name` attribute to `swift_c_module`.
Add `module_name` attribute to `swift_c_module`.

This will be mandatory to support precompiled modules, since the `swift_c_module` target is where precompilation will occur. Therefore, targets with module maps that define multiple modules will need to be split into multiple targets, each referencing a single module name and the appropriate subset of headers for that module.

RELNOTES: None.
PiperOrigin-RevId: 296432701

bazelbuild/rules_swift,bazelbuild/rules_swift