[bugfix] Fix hook execution order for hooks in the same class

[vkarak]

This was practically introduced because we blindly reversed the order of hooks in RegressionTest.pipeline_hooks(). Now the reverse MRO order is ensured as we build the global hook registry of the class. Since the local registries of the parent classes are used to update this class' registry, the order of their hooks as they are inserted is preserved.

Fixes #2284.

[codecov-commenter]

Codecov Report

Merging #2287 (bd4c5ae) into master (30346e0) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2287   +/-   ##
=======================================
  Coverage   86.12%   86.12%           
=======================================
  Files          56       56           
  Lines       10206    10208    +2     
=======================================
+ Hits         8790     8792    +2     
  Misses       1416     1416           

Impacted Files	Coverage Δ
reframe/core/hooks.py	90.00% <100.00%> (+0.22%)	⬆️
reframe/core/meta.py	98.80% <100.00%> (ø)
reframe/core/pipeline.py	92.83% <100.00%> (ø)

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