Add CLI commands for detecting and remove dead code

[Morriar]

Run dead code detection in your project with:

$ spoom deadcode

This will list all the methods and constants that do not appear to be used in your project.

Collecting files...
Indexing 122 files...
Analyzing 1033 definitions against 1128 references...

Candidates:
  Spoom::LSP::ResponseError::data lib/spoom/sorbet/lsp/errors.rb:47:18-47:23
  Spoom::Deadcode::Remover::NodeRemover::delete_line_part lib/spoom/deadcode/remover.rb:300:8-312:11
  Spoom::Deadcode::Indexer::file_name lib/spoom/deadcode/indexer.rb:10:25-10:35
  Spoom::LSP::Notification::method lib/spoom/sorbet/lsp/base.rb:62:18-62:25

  Found 5 dead candidates

You can remove them with Spoom:

$ spoom deadcode remove lib/spoom/sorbet/lsp/errors.rb:47:18-47:23

This will delete the dead code and show you the resulting diff:

@@ -43,9 +43,6 @@
       sig { returns(Integer) }
       attr_reader :code

-      sig { returns(T::Hash[T.untyped, T.untyped]) }
-      attr_reader :data
-
       class << self
         extend T::Sig