x/tools/gopls: release version v0.19.0

[gopherbot]

This issue tracks progress toward releasing gopls@v0.19.0

• create or update gopls-release-branch.0.19
• update go.mod/go.sum (remove x/tools replace, update x/tools version)
• tag gopls/v0.19.0-pre.1
• update Github milestone
• write release notes
• smoke test features
• tag gopls/v0.19.0
• (if vX.Y.0 release): update dependencies in master for the next release

[gopherbot]

Change https://go.dev/cl/678615 mentions this issue: all: update codereview.cfg for gopls-release-branch.0.19

[adonovan]

TODO:

• land CL 678595 (small fix to "eliminate dot import")
• land CL 678475 (enable new import machinery; needs cherrypicking)

[gopherbot]

Change https://go.dev/cl/678616 mentions this issue: gopls: update go.mod for v0.19.0-pre.1

[gopherbot]

Change https://go.dev/cl/678735 mentions this issue: extension: update gopls v0.19.0-pre.1 settings

[gopherbot]

Change https://go.dev/cl/678759 mentions this issue: gopls/doc/release: tweak v0.19

[gopherbot]

Change https://go.dev/cl/678760 mentions this issue: all: merge master (82473ce) into gopls-release-branch.0.19