Resolve "Use the new Enum for CommitDiff RPC"

What does this MR do and why?

Related to issue: #378213 (closed)

Related to epic: &9028 (closed)

The Gitaly team introduced a new enum to the diff_commit RPC where we can now ignore all the white space.

Steps to reproduce

1. Add and commit this a file called TESTFILE with the following contents into a repository:

   Leading whitespace with tab 1
   Leading whitespace with space 2
   Trailing whitespace with tab 3
   Trailing whitespace with space 4

2. Make a new branch. Eg. whitespace-test

3. Replace TESTFILE with the following contents (Note the leading/trailing whitespace changes as well):

           Leading whitespace with tab 1
    Leading whitespace with space 2
   Trailing whitespace with tab 3	
   Trailing whitespace with space 4 

4. Create a new MR from this branch.

5. Look at the diff with Show Whitespace changes both on and off, observe that whitespace changes with leading whitespace are always displayed.

6. Turn on the Feature flag: add_ignore_all_white_spaces

7. Observe that no changes are shown NOTE, a frontend issue is still needed to be completed before we can turn on the Feature flag.