x/tools/gopls: initial support for pull-based diagnostics available in LSP 3.17

[hyangah]

LSP 3.17 adds support for Pull Diagnostics

The spec includes Document Diagnostics, Workspace Diagnostics.

I think this allows us to address some long-standing issues like

• gopls: support a setting to control the frequency of diagnostics vscode-go#50 Support a setting to control the frequency of diagnostics
  (some users want to see diagnostics only when they save a file, not as they type
• Option to run diagnostics only on current package vscode-go#1275 Option to run diagnostics only on current package

Partly

• x/tools/gopls: support features (diagnostics, etc.) for open files inside of vendor directories #42527 Support diagnostics for files inside vendor directories
• x/tools/gopls: don't show analysis for std and 3rd-party packages #45607 (comment) Fine-grained control on diagnostics

[gopherbot]

Change https://go.dev/cl/611843 mentions this issue: gopls/internal/cache: join concurrent package batch operations

[gopherbot]

Change https://go.dev/cl/616835 mentions this issue: gopls: add initial support for pull diagnostics