refactor: ts helpers (#568)

* handle different quotes for string literal types

* refactor find methods to return an object in place of an array

* fix broken tests

* refactor hasTypeProps, remove hasTypeProp, fix broken tests

* implement Oliver's suggestions

* always return a sourceFile, unwrap single-statement sourceFiles

* add getBody

* feat: allow direct chaining without getBody

* refactor: stylistic cleanup

* add test for variables nested in arrow functions

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Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

Author: Dario-DC