fix(thumbor): allow watermarks in folders for thumbor requests

[dougtoppin]

thumbor style requests including a watermark in a folder failed with watermark key not found error.
The parseImageKey regex failed to detect the watermark key correctly due to the embedded slash.
This changes the regex to detect the watermark correctly and includes new unit tests for that case.

Example thumbor style request with watermark in folder/key.png:
/fit-in/400x400/filters:watermark(bucket,folder/key.png,0,0)/image.jpg

Description of changes:

• image-request/parseImageKey regex addition for watermark inclusion
• unit tests for image-request, thumbor-mapper to verify watermarks with and without folder

Checklist

• 👋 I have added unit tests for all code changes.
• 👋 I have run the unit tests, and all unit tests have passed.
• ⚠️ This pull request might incur a breaking change.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[CrypticCabub]

the CodeQL stuff seems nice to have, though the errors do also make it a little harder to review if they are supposed to be supressed.