REGEX frontend: white space and nesting bugfix

[reuterbal]

Discovered with IFS source files.

Two small fixes for the REGEX frontend patterns, with tests that triggered before the corresponding changes:

• Multiple or no white space around the end statement for procedures
• Matching of module procedures is now lazy to match internal subprograms in module procedures

[github-actions]

Documentation for this branch can be viewed at https://sites.ecmwf.int/docs/loki/274/index.html

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.83%. Comparing base (6b58fe7) to head (92c0c5c).
Report is 32 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #274   +/-   ##
=======================================
  Coverage   92.83%   92.83%           
=======================================
  Files         102      102           
  Lines       18121    18121           
=======================================
  Hits        16823    16823           
  Misses       1298     1298           

Flag	Coverage Δ
lint_rules	96.39% <ø> (ø)
loki	92.80% <ø> (ø)
transformations	92.20% <ø> (ø)

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[mlange05]

Looks good to me and behaves correctly with ec-physics regression. GTG