feat: add getPackageAvailableVersions to public API and bump API to 1.1.0

[edvilme]

Summary

• add PythonPackageGetterApi.getPackageAvailableVersions to the public API so consumers can query a package's available versions
• bump @vscode/python-environments from 1.0.0 to 1.1.0
• synchronize both API lockfile version fields
• document the public API changes since the latest npm release

API changes

• add PythonPackageGetterApi.getPackageAvailableVersions(environment, packageName): Promise<Pep440Version[] | undefined> — exposes a package's available versions (newest-first) to API consumers, delegating to the environment's package manager and resolving to undefined when version listing is unsupported
• re-export Pep440Version for package manager version APIs
• add PackageInfo.isTransitive and GetPackagesOptions.skipCache
• add optional package manager hooks for watch targets, direct dependencies, tool versions, available package versions, and install-spec formatting
• add the optional GetPackagesOptions parameter to PackageManager.getPackages and PythonPackageGetterApi.getPackages
• update PackageManager.refresh and PythonPackageGetterApi.refreshPackages to return the refreshed package list when available

Validation

• npm run lint
• npm run compile-tests
• npm run unittest (1494 passing, 5 pending)
• git diff --check

[edvilme]

Adding "skip tests" label since this functionality already exists but is now being exposed to the public API