Move utilities used for the Diffs app Tree Worker into a separate file

What does this MR do?

Since the Tree Worker operates in a Web Worker context, it makes sense to separate it from the rest of the utilities so that imports that rely on things like window don't break the Worker script.

Context

I'm adding a utility that computes the humanized bytes of a diff file to the diff file utility and - by relying on window- the mere presence of the humanization import breaks the entire Diffs app because the utility file is imported into a Web Worker for other utilities it exports.

Screenshots (strongly suggested)

N/A, all backstage

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.