Refactor - LoadedPrograms part 2

[Lichtso]

Problem

General fixes split off from #33477, continuation of #33482.

Summary of Changes

• Uses one mock environment across all entries generated in each LoadedProgram test.
• Adds LoadedProgramType::get_environment().
• Adjusts test_runtime_feature_enable_with_program_cache().
• Filter out entries of different environments in LoadedPrograms::extract().
• Adds LoadedPrograms::get_environments_for_epoch().

[codecov]

Codecov Report

Merging #33694 (64038d2) into master (09e858d) will decrease coverage by 0.1%.
The diff coverage is 92.1%.

@@            Coverage Diff            @@
##           master   #33694     +/-   ##
=========================================
- Coverage    81.8%    81.8%   -0.1%     
=========================================
  Files         806      806             
  Lines      217676   217684      +8     
=========================================
- Hits       178220   178217      -3     
- Misses      39456    39467     +11