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 64.15%. Comparing base (3c75d75) to head (9091af6).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1454      +/-   ##
===========================================
+ Coverage    62.70%   64.15%   +1.44%     
===========================================
  Files           51       51              
  Lines         4073     4073              
  Branches       356      356              
===========================================
+ Hits          2554     2613      +59     
+ Misses        1489     1430      -59     
  Partials        30       30              

see 2 files with indirect coverage changes

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