* Add tests for action parsing.
[skip ci]
* Fix action parsing issues.
Related issues: #2088.
* Simplify action parsing.
Turns out that we can just wrap the string that we want to parse as the arguments in '({string_here},)', as per @willmcgugan's comment in the PR review.
Related review comments: https://github.com/Textualize/textual/pull/2112\#issuecomment-1481015988
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Co-authored-by: Will McGugan <willmcgugan@gmail.com>
