internal/lsp/cache: add a scheme for types error code links
internal/lsp/cache: add a scheme for types error code links

Links in the new LSP diagnostic CodeDescription for go/types errors are
missing a scheme (unclear why they work in some clients). Fix this by
delegating to the existing source.BuildLink helper (this also adds the
utm_source query parameter for pkg.go.dev).

Fixes golang/go#44360

Change-Id: Ife8969f32bb11840c0fdd31765b6051b3d997a93
Reviewed-on: https://go-review.googlesource.com/c/tools/+/293509
Trust: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
Trust: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools