Add code action support to the ruby-lsp

[vinistock]

Code actions provide the ability to define any type of refactor that developers can manually apply. Some examples:

• Extract to method: select a portion of the code and have it extracted into a private method with the right parameters
• Make a method private
• Move method to parent class
• Change a block from do - end to {} Add switch block refactor #2372
• Change a single line invocation to multiline
• Change if to unless
• Change while to until
• Wrap class in module
• Add attr_reader, attr_writer or attr_accessor for a given instance variable

Documentation: https://microsoft.github.io/language-server-protocol/specification#textDocument_codeAction

[st0012]

With locals information provides by ruby-syntax-tree/syntax_tree#157, we should be able to achieve inline local variables (example from RubyMine) relative easily.