feat: add workspace diagnostic support

[karthiknadig]

Description (e.g. "Related to ...", etc.)

Adds workspace diagnostic request support.

Code review checklist (for code reviewer to complete)

• [x] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• [x] Title summarizes what is changing
• [x] Commit messages are meaningful (see this for details)
• [x] Tests have been included and/or updated, as appropriate
• [x] Docstrings have been included and/or updated, as appropriate
• [x] Standalone docs have been updated accordingly

[tombh]

Does this contribute to LSP 3.17 support? We've got a tracking issue at https://github.com/openlawlibrary/pygls/issues/346

[karthiknadig]

@tombh Yes. The diagnostics had two parts document diagnostics and workspace diagnostics. My Previous PR (https://github.com/openlawlibrary/pygls/pull/360) added document diagnostic. This one adds the workspace diagnostic.

[tombh]

Thank you ✨