This PR adds a hacky way of generating and then installing the .cms files for the compiler alongside the .cmt files. As a result, a subset of the .cms files will subsequently be picked up by the per-file format metrics. Currently, there are 797 .cmt files that we install, but this PR only adds 352 .cms files. See the considerations below.

Considerations

• The .cms files are generated and installed unconditionally at the moment. The size of all of the 352 files is currently ~4 MB. For comparison, the 797 .cmt files are currently ~376 MB.
• This is only a best-effort approach. To properly install the .cms files, dune would have to support -bin-annot-cms. Even with the current hack, there are many .cmt files that don't have corresponding .cms files as noted above.
• Once this is merged, the compiler (for debug information) and likely also Merlin will pick up the .cms files rather than the .cmt files from the installation.
• The PR contains tweaks for various dune files that were not compiled with our flags before.