Change filenames in test cases.

[JustinKyleJames]

• 4-3-stable
• main

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There are a lot of test cases where the filename that is created is "f1" or "f2".

In more recent tests I've used the following pattern:

file1 = f'{inspect.currentframe().f_code.co_name}_f1'

Change all the references from f1 and f2 to this. It's an easy search and replace and it provides a little extra debug information.

This will only be done for 4.3 / main branches as the above code only works in Python 3.

[JustinKyleJames]

This has been merged into both main and 4-3-stable. It will not be merged into 4-2-stable as this code uses Python 3 specific features.