[rtemodel] Adjust default heap in regions file according to total RAM (#1010)

[grasci-arm]

Address #1675

[github-actions]

Test Results

  6 files   12 suites   8s ⏱️
 35 tests  35 ✅ 0 💤 0 ❌
105 runs  105 ✅ 0 💤 0 ❌

Results for commit 6d488ed.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.89%. Comparing base (22e5047) to head (6d488ed).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1729   +/-   ##
=======================================
  Coverage   63.89%   63.89%           
=======================================
  Files         162      162           
  Lines       31768    31768           
  Branches    19474    19474           
=======================================
  Hits        20298    20298           
- Misses       7552     7554    +2     
+ Partials     3918     3916    -2     

Flag	Coverage Δ
buildmgr-cov	74.21% <ø> (ø)
packchk-cov	65.54% <ø> (ø)
projmgr-cov	80.62% <ø> (ø)

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see 8 files with indirect coverage changes