gopls: added method docs to hover info

[tobigiwa]

The change also includes a jump to definition feature for all methods.The change is quite fail-safe, such that if it fails in any way, it will still display the hover info without the method docs(as before). The change is localised to the the gopls/internal/golang/hover.go file, in function hover and formatHover.
I should also mention that it does not alter the method displayed or it order, it just add the method docs (if any) and a jump to page source url to the hover info.

Fixes golang/go#66721
Fixes golang/go#66721

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Message from Gopher Robot:

Patch Set 1:

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