Spack changes for laghos/remhos and their dependencies

[rfhaque]

Description

This PR adds changes to the spack packages for laghos and remhos and their dependencies in preparation to upstream to the spack-packages repository. The PR

• Adds support for c++20 to the cce compiler (required for RAJA)
• Adds support for the develop versions of RAJA, Umpire and camp
• Adds a variant to use the default GPU stream in camp. Depends on Add cmake option for CAMP_USE_PLATFORM_DEFAULT_STREAM camp#205

Adding/modifying a benchmark (docs: Adding a Benchmark)

• If package.py upstreamed to Spack is insufficient, add/modify repo/benchmark_name/package.py plus: create, self-assign, and link here a follow up issue with a link to the PR in the Spack repo.
• Add/modify an experiments/benchmark_name/experiment.py to define an experiment

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.40%. Comparing base (868acb3) to head (a5e1428).

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #1454       +/-   ##
============================================
+ Coverage    50.07%   63.40%   +13.33%     
============================================
  Files           29       49       +20     
  Lines         2093     3913     +1820     
  Branches       341      341               
============================================
+ Hits          1048     2481     +1433     
- Misses         972     1412      +440     
+ Partials        73       20       -53     

see 32 files with indirect coverage changes

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