feat(vscode): allow the lsp loaded to be specified

[benfdking]

• allow the extension to specify the lsp script entrypoint
• tests the different scenarios
  • absolute entrypoint
  • relative entrypoint
  • entrypoint with arguments

[Copilot]

Pull Request Overview

This PR adds LSP entrypoint configuration support to the VSCode SQLMesh extension, allowing users to specify a custom LSP server command instead of using the default sqlmesh_lsp binary.

• Adds a new sqlmesh.lspEntrypoint configuration option that accepts a command with optional arguments
• Modifies the LSP execution logic to prioritize the configured entrypoint over the default discovery
• Includes comprehensive test coverage for absolute paths, relative paths, and entrypoints with arguments

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
package.json	Adds the new sqlmesh.lspEntrypoint configuration property
src/utilities/config.ts	Implements parsing logic for the LSP entrypoint configuration
src/utilities/sqlmesh/sqlmesh.ts	Updates LSP execution to use configured entrypoint when available
tests/configuration.spec.ts	Adds test cases covering different entrypoint configuration scenarios