add search for environment UX feature

[eleanorjboyd]

new feature that allows users to easily discover environments and configure their discovery settings.

• a new icon in the env manager widget next to the "create environment" plus button, this icon is a search one
• when a user clicks on this they get a dropdown:

1. adjust search path settings
2. do full workspace search

1: adjust

• this will open the settings editor with the search "search path" and extension for "python-envs" to show the globalSearchPath and workspaceSearchPath options

2. do full search

• this will trigger a brand new search in the whole workspace (so root/*) so it looks everywhere in the workspace. This you can pass to PET when calling the native finder since that supports grep. It will then load all the envs it finds
• afterwords- give a new popup "save this search setting"
• either yes, no, don't show again
• if yes, adjust the workspaceSearchPath to be root/* or whatever so all new envs they add to the workspace are discovered. if the user already has searchPaths, append. If user already has root/* don't append it twice

[eleanorjboyd]

went a different direction with the actual PR:

This PR introduces a settings icon to the Environment Manager view that opens workspace-level search settings, and changes the default workspace search path from an empty array to ["./**/.venv"] to enable automatic discovery of .venv folders in workspaces.

Changes:

Adds a gear icon button to the env-managers view that opens search path configuration
Sets default workspace search path to ./**/.venv for automatic venv discovery
Updates getWorkspaceSearchPaths() to use default values from package.json when no workspace-specific config exists