Add basic pytest tests for umdp3_conformance.py (#216)

* Yet another weird round of having to repeatedly accept the same changes which git / VS Code are marking as in conflict.
Annoyingly, this seems to have introduced a bug as well.

* Fixing issue with external runners not establishing properly.

* Fixing an error that seems to have crept in during merging main and resolving clashes. But looking at it, I really can't fathom out 'how'

* Where do these line length errors in the linter(s) come from - I haven't edited this file...

* quick "improvement" to the error reporting in one of the tests

* Why am I constantly having to re-impliment fixes/tidying I'm sure I've done before.

* And now ruff_format wants to change them back again...

* Add some basic tests

* Using suggestions from CoPilot, inseret what it considers the high priority checks missing from umdp3_conformance.py. That was fun

* ScoobyDoobyDOOOOoooooooo

* Minor tweak to output text that seems to have got lost in previous branches.

* Tweaking the tests and taking suggestions from CoPilot for further tests - I think the power has gone to it's head...

* adapting to the latest crazy linting settings

* move the type ignore comment which the autoformatter shifted to the next line where it no longer works...

* Oh look ma - the linter didn't like the change made to appease the formatter, or was it the other way round...

* Adding a copyright statement

Co-authored-by: Erica Neininger <107684099+ericaneininger@users.noreply.github.com>

* Adding other missing copyright statements

---------

Co-authored-by: Erica Neininger <107684099+ericaneininger@users.noreply.github.com>

Author: r-sharp

script_umdp3_checker/tests/test_fortran_checks.py

@@ -1,3 +1,9 @@
+# -----------------------------------------------------------------------------
+# (C) Crown copyright Met Office. All rights reserved.
+# The file LICENCE, distributed with this code, contains details of the terms
+# under which the code may be used.
+# -----------------------------------------------------------------------------
+
 import pytest
 import sys
 from pathlib import Path