UNST-9674: remove obsolete keywords 2nd try

[thomas-pijls]

What was done

2nd try at removing all the obsolete keywords from the testbench.

• Added many (very old) keywords to the obsolete list in fm_deprecated_keywords.f90
• Removed the obsolete keywords from the unit test mdu's

Not yet done:

• Removed the obsolete keywords from all mdu's in the testbench

Evidence of the work done

• Video/figures
  <add video/figures if applicable>
• Clear from the issue description
• Not applicable

Tests

• Tests updated
  <add testcase numbers if applicable, Issue number>
• Not applicable

Documentation

• Documentation updated
  <add description of changes if applicable, Issue number>
• Not applicable

Issue link