x/tools/gopls: compute references/refactoring for all build configurations

[findleyr]

This issue follows up on zero-config gopls (#57979). With that change, gopls can dynamically add build configurations (Views) to work on, as files are opened and closed.

But for performance reasons, gopls does not load all build configurations: go list can take upwards of 10s, and there are ~50 supported ports.

However, when performing a workspace-wide refactoring such as renaming, or even while finding references, we should consider analyzing all workspace files to compute the set of required build configurations, and applying the refactoring for these configurations, since this is likely a much smaller set.

CC @adonovan @suzmue