Reduce the size of the _FoundationCollections toolchain module

[jmschonfeld]

The number of object files in the single _FoundationCollections toolchain module was causing issues on Windows by surpassing the maximum command line invocation length. To work around this for now, we reduce the size of the module by not including certain sub-modules. This will unblock the swift-foundation re-core work. At a later time, we could come back to adjust the CMake build to use response files to avoid a large command line invocation if necessary as a full solution.

Checklist

• [x] I've read the Contribution Guidelines
• [x] My contributions are licensed under the Swift license.
• [x] I've followed the coding style of the rest of the project.
• [x] I've added tests covering all new code paths my change adds to the project (if appropriate).
• [x] I've added benchmarks covering new functionality (if appropriate).
• [x] I've verified that my change does not break any existing tests or introduce unexplained benchmark regressions.
• [x] I've updated the documentation if necessary.