x/tools/gopls: orphaned file reloading causes unnecessary loads

[findleyr]

The current logic of reloadOrphanedFiles causes it to reload irrelevant files in the workspace, once they have been mapped (e.g. because of a branch change).

More generally, we should avoid ever ranging snapshot.files, as it is the set of files previously seen by the snapshot, which is path-dependent and has no intrinsic meaning.

CC @adonovan

[gopherbot]

Change https://go.dev/cl/454559 mentions this issue: gopls/internal/lsp/cache: narrow reloadOrphanedFiles to open files

[findleyr]

I'm going to close this as reloading open files is an acceptable operation. Reloading every known file is not.

It would still be nice to eliminate reloading entirely.