Account for lowercase drive letter on Windows

[gifvex]

Motivation

The recent release of Shopify/vscode-ruby-lsp@53fb04a made the extension work on Windows. On Windows, VS Code can spawn the terminal used by extensions with a lowecase drive letter, which causes the following error and prevents the extension from starting:
URI::InvalidComponentError: bad component(expected absolute path component): c:/some/windows/path/to/file.rb

Implementation

The drive pattern introduced in #850 was switched to case-insensitive.

Automated Tests

The tests also introduced in #850 were expanded to cover lowercase drive letters.

[gifvex]

I have signed the CLA!

[gifvex]

Update pushed; moved the CGI.unescape in to_standardized_path to happen before the regex looks for a colon.

ruby-lsp/lib/ruby_lsp/requests/diagnostics.rb

Lines 39 to 40 in fb16059

	path = @uri.to_standardized_path
	return unless path.nil? || path.start_with?(T.must(WORKSPACE_URI.to_standardized_path))

The check here to run rubocop failed because the language server protocol can send escaped colons (example @ learn.microsoft.com) and the added / wasn't being removed.

[vinistock]

Thank you very much for the contribution!