Incorporate API and Behavior feedback on the environment manager extension

[karthiknadig]

### APIs for python environment:
- [x] API for create/remove environments provider
- [x] API for environment discovery, collection, and change
- [x] API for selection and selection change
- [x] API for package list and package list change
- [x] API for package install/remove
- [x] API to add/remove folders or scripts with custom environments
- [x] API to identify a given path to an environment
- [x] API for Shell specific activation commands
- [x] API for custom arguments to Install/Remove packages
- [ ] ~API for custom arguments to create/remove environments~

### Environment management behavior:
- [x] Show environment for the selected item in the status bar
- [x] Show button to add folder in file explorer
- [x] Show button to select environment in the file explorer view (on python binaries and on environment folders)
- [x] shell specific activation commands
- [x] clear cache command
- [x] Remove package manager selection while selecting env manager
- [x] Only selected env manager is initialized
- [x] File system watcher for envs.

### Env Manager Contributions:
- [x] Use `pet` to provide data for environments
- [x] Selection Caching
- [x] Conda env manager (demo support)
- [x] System (built in)
- [x] venv (built in)
- [x] Uv (if available)

### Package Manager Contributions:
- [x] pip (built in)
- [x] conda (demo support)
- [x] uv (if available built-in)