The legacy `module.map` spelling of module map files was deprecated by llvm/llvm-project#75142 and clang expects to remove support for them in the future. Switch all tests to use the supported spelling.
Fixes rdar://128431478.
`module.map` as a module map name has been discouraged since 2014, and
Clang will soon warn on its usage. This patch renames all instances of
`module.map` in the Swift tests to `module.modulemap` in preparation
for this change to Clang.
rdar://106123303
