Add support of the FORALL statement and construct (fparser/fgen)

[quepas]

This pull request adds support of the FORALL statement and construct: Intel Developer Reference - FORALL. Adding the FORALL support has been mentioned in #117.

I tried to mimic your coding style as much as possible. I am looking forward to your review!

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.79006% with 4 lines in your changes missing coverage. Please review.

Project coverage is 95.27%. Comparing base (a39336b) to head (87082db).

Files	Patch %	Lines
loki/frontend/omni.py	88.88%	2 Missing :warning:
loki/frontend/fparser.py	95.65%	1 Missing :warning:
loki/ir/nodes.py	94.73%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #210      +/-   ##
==========================================
+ Coverage   95.25%   95.27%   +0.01%     
==========================================
  Files         170      170              
  Lines       36258    36438     +180     
==========================================
+ Hits        34539    34715     +176     
- Misses       1719     1723       +4     

Flag	Coverage Δ
lint_rules	96.39% <ø> (ø)
loki	95.25% <97.79%> (+0.01%)	:arrow_up:

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[quepas]

@reuterbal I have added some unit test of the Forall statement/construct. I will try to work on the Forall support in OFP/OMNI parsers soon as well :)

[reuterbal]

Apologies for the delay in getting back to this. I have fixed the tests and added (limited) support for Forall to the other frontends. OMNI seems to be doing entirely stupid things but OFP can at least parse two out of three test cases.

@quepas: Please have a look if this looks ok to you.

Thanks!

[quepas]

It looks great! Sorry for the lack of activity from my side on this pull request. I tried to program the FORALL for the OFP, but I failed initially :P