Update minimal python and dbconnect versions for serverless

[misha-db]

Changes

• package.json — Added databricks.connect.serverlessDbconnectVersion setting (default "17.3")
• WorkspaceConfigs.ts — Added serverlessDbconnectVersion getter reading the new setting
• EnvironmentDependenciesVerifier.ts:
  • checkPythonEnvironment: replaces hardcoded [15, 1] with DBR version derived from serverlessDbconnectVersion; min Python minor is 12 for major ≥ 16, else 11
  • checkDatabricksConnectVersion: bumps min serverless version from < 15.1 to < 15.4 and updates the error message
    EnvironmentDependenciesInstaller.ts:
  • getSuggestedVersion: replaces hardcoded "15.1." with ".." derived from serverlessDbconnectVersion

Tests

Manual

[github-actions]

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Trigger:
go/deco-tests-run/vscode

Inputs:

• PR number: 1884
• Commit SHA: 699789f569d8ddaf6f1e839579233b5c79a49209

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