Replace findloc() with user-defined find_index

[marshallward]

This patch replaces the instances of findloc() with a new function,
find_index. They should be functionally equivalent.

findloc() is a F2008 intrinsic which returns the index of the first
instance of a value in an array. Support is still spotty on some older
compilers in active use, so this function is the safer alternative.

[codecov]

Codecov Report

Merging #136 (d94237a) into dev/gfdl (37782eb) will not change coverage.
The diff coverage is n/a.

❗ Current head d94237a differs from pull request most recent head 636d220. Consider uploading reports for the commit 636d220 to get more accurate results

@@            Coverage Diff            @@
##           dev/gfdl     #136   +/-   ##
=========================================
  Coverage     33.45%   33.45%           
=========================================
  Files           262      262           
  Lines         71385    71385           
  Branches      13323    13323           
=========================================
  Hits          23884    23884           
  Misses        43029    43029           
  Partials       4472     4472           

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[marshallward]

This PR is required in order to switch the CI to the FMS2 infra (NOAA-GFDL/MOM6-examples#353).

[adcroft]

Pending https://gitlab.gfdl.noaa.gov/ogrp/MOM6/-/pipelines/15675 (and prior PRs)

[marshallward]

Sorry this PR was broken and does not even compile. Will submit a patch ASAP...

[adcroft]

It did compile, and ran fine! https://gitlab.gfdl.noaa.gov/ogrp/MOM6/-/pipelines/15675

[marshallward]

Indeed, garbage commits to the FMS2 infra do not break the FMS1 build 🤣