Enable "toggle block style" refactor when there's no selection

[rolandcrosby-columntax]

Motivation

The "toggle block style" refactor action currently only works if there is a selection in the editor which covers a call node and its associated block. When there's no selection but the cursor is inside a block, it would be nice to be able to toggle the style of the block that the cursor is inside.

Implementation

• In the CodeActions request: add a quick check using @document.locate_node to conditionally offer the "toggle block style" action if the cursor is inside a BlockNode
• In the CodeActionResolve request: add a similar call to find the current block node when there's no selection. The actual rewrite also needs the CallNode associated with the block, and I couldn't figure out a good way to do this without adding a second RubyDocument.locate call. (When you call locate_node to get the BlockNode, you don't get any reference to the CallNode that the BlockNode is attached to. You also can't just look for a CallNode covering the cursor - that could return a CallNode that's actually inside the block that you want to toggle.)

Automated Tests

Added some expectation tests:

• verify that the code action is offered when the cursor is inside a block and isn't offered when the cursor is outside a block
• verify that the rewrite action toggles the expected block(s) depending on the cursor position

Manual Tests

• Place your cursor outside a block and trigger code actions => none should be available.
• Place your cursor inside a block and trigger code actions => "Refactor: Toggle block style" should be available, and should toggle the style of the block that the cursor is inside (and any nested blocks)

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[rolandcrosby-columntax]

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