fix: MockFile - clone the bytes in read/write allbytes methods

[jamesmoore]

What is this doing?

• When reading from the MockFile's content with the ReadAllBytes method return a copy of the content, not a reference to the content itself.
• When writing to the MockFile content update it with a copy of the new content, not a reference to the new content.

Why are we doing this?

These Read/WriteAllBytes should be result in two instances of the file content - one on the mock filesystem and the in-memory instance.

How was it tested?

Unit tests to ensure there are two independent instances of the content after each operation.

[siprbaum]

Looks good to me.

[fgreinacher]

Thanks @jamesmoore 👍

[github-actions]

This is addressed in release v17.0.18.