feat: remove `environment` library and deprecate `--protocol` flag

Motivation and Context

Following on from !3142 (merged), we noticed that the environment and --protocol flag are no-longer necessary (since we only support a given protocol at a given version).

Description

This MR removes the environment library and deprecates the --protocol flag.

Component

• compiler
• website
• webide
• vscode-plugin
• debugger

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance improvement (non-breaking change that improves performance)
• None (change with no changelog)

Changelog

Deprecate the --protocol flag.

ligo compile contract unit.mligo --protocol parisb
Warning: the flag `-p` (aliases: `--protocol`) is deprecated and will be ignored
  { parameter unit ;
    storage unit ;
    code { DROP ; UNIT ; NIL operation ; PAIR } }

Checklist:

• If a new syntax has been introduced, put a message on slack ligo-lsp
• Changes follow the existing coding style (use dune @fmt to check).
• Tests for the changes have been added (for bug fixes / feature).
• Documentation has been updated.
• Changelog description has been added (if appropriate).
• Start titles under ## Changelog section with #### (if appropriate).
• There is no image or uploaded file in changelog
• Examples in changed behaviour have been added to the changelog (for breaking change / feature).