Fix settings reconciliation for nested properties

[krassowski]

References

Fixes #1047

Code changes

pyright's python.analysis.diagnosticSeverityOverrides is a bit different from most settings because it is an object.
Prior to these PR we were allowing both dotted and nested specification of settings, and always normalized to the fully dotted notation. However, the settings schema for python.analysis.diagnosticSeverityOverrides was defined as an object, and UI settings were reverting it to an object leading to conflicts.

This PR:

• changes the normalization rules so that we normalize to format aligned with config schema
• ensures reconciliation of settings across different sources works correctly by adding appropriate jest tests (some code gets extracted to a static method to make it easier to test)
• updates pyright schema to v1.1.350
• avoids confusing setting duplication by preventing leakage of rank and configuration which are now only set on a copy where needed

User-facing changes

python.analysis.diagnosticSeverityOverrides can be configured in overrides.json or changed in settings without conflicts upon reloading JuypterLab.

Backwards-incompatible changes

None

[github-actions]

👈 Launch a binder notebook on branch krassowski/jupyterlab-lsp/fix-settings-reconciliation