Transform '_WORKLET' in worklets to 'true'.

[tjzel]

Summary

The goal of this PR is to add functionality of changing UI runtime checks (aka _WORKLET) to true in worklets, an extension to/alternate solution of #4511.

Notice that in the code I'm not traversing the worklet's tree to get _WORKLET nodes to change them to true - I'm just replacing substrings in worklet's code.

The reason of that is the fact we don't have trees for worklets - only a given node and its code. We could change them into ASTs and then replace certain nodes, but this seems unnecessary according to my research - we would need to do following steps:

1. Clone the node for future worklet (we already do that).
2. Generate code for the node (we already do that).
3. Parse generated code to AST.
4. Traverse AST and replace certain nodes.
5. Generate code from AST.

Those could be some time-consuming extra steps that don't seem to be really needed, since we expect every _WORKLET in worklet's code to be a part of a boolean expression.

Things I also did in this PR:

• Small refactor of plugin tests - moved comments into describe blocks (it just makes much more sense that way).
• Moved commonly used unions of types from plugin into their own type alias.

TODO:

• Transform _WORKLET in non-worklets to false (probably, since I think I remember that was the chief issue).

Test plan

I've added a whole new test suite for this functionality in plugins tests. Also ran Example app to see if it works properly.

[tjzel]

RIP in peace