x/tools/gopls: show all methods on hover (not just explicit methods)

[findleyr]

Forking from #54008 (comment), where @oneliey suggested that we show all methods on hover, not just explicit methods.

After using this new hover feature for a bit, I agree with that assessment. It is more useful to see all available methods. Does anyone disagree?

[gopherbot]

Change https://go.dev/cl/555456 mentions this issue: gopls/internal/lsp/source: show promoted methods in hover