Support singleton server instance or workspace-folder configuration for multi-root workspaces

Problem

Extensions such as vscode-pylint (see vscode-pylint#476) spawn a Language Server process (e.g. lsp_server.py) for every folder in a multi-root workspace, even when these folders share the same configuration or interpreter. This is the default behavior in VS Code extensions, but leads to redundant processes, duplicated linting (and logs/diagnostics), and unnecessary resource usage in projects with many folders.

Currently, vscode-common-python-lsp provides utilities for settings resolution and server lifecycle, but it still assumes and implements a one-client-per-workspace-folder model and does not provide a mechanism to:

• Start one language server across all folders (when appropriate)
• Avoid redundant or duplicate LSP processes for subfolders
• Allow the user to configure (disable) tool extensions per workspace folder (e.g., simulate a tool.enable = false setting)

Request

• Add first-class support for more advanced multi-root workspace scenarios:
  • Option 1: Support a singleton LanguageClient/Language Server mode across multiple folders with compatible config/interpreter
  • Option 2: Provide APIs/utilities or recommended patterns to allow extension authors to implement per-folder enable/disable logic (e.g., pylint.enable: false)
• Optionally, add sample code and documentation for how to prevent duplicate processes or respect per-folder settings.

Example motivating issue

See original problem and user request: https://github.com/microsoft/vscode-pylint/issues/476

Notes

• This would benefit all Python tool extensions consuming this library, not just pylint.
• If implemented here, it would encourage consistency and reduce redundant issue reports/upstream maintenance.

Thanks for considering!