Fix Regression: interpreter selection status bar not working when switching environments

[StellaHuang95]

fixes #1124

The changes made in #1120 introduced logic to avoid writing unnecessary settings when the selected environment manager is the implicit default (system manager). This was intended to prevent polluting settings.json.

However, this optimization broke manual interpreter selection. When a user clicks the status bar and explicitly selects a global/system interpreter in a workspace with an empty settings.json, the selection is silently ignored because the code determines "this is the default, so don't write it."

This PR added an optional forceWrite flag to EditAllManagerSettings, EditEnvManagerSettings, and EditPackageManagerSettings interfaces and updated all user-initiated callers in envManagers.ts and envCommands.ts to pass forceWrite: true.