[feat] Allow the -P option to redefine existing parameters

[vkarak]

To achieve this we add type information to parameters, so that the user-supplied arguments can be correctly converted by the test. The change is seamless, as by default no type information is required for parameters, but if users want to re-parameterize a test, then the parameters must have a type.

Closes #2674.

Todos

• Update the docs

[codecov]

Codecov Report

❌ Patch coverage is 93.10345% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.23%. Comparing base (df31923) to head (a32c19b).
⚠️ Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
reframe/frontend/testgenerators.py	92.45%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3554   +/-   ##
========================================
  Coverage    91.22%   91.23%           
========================================
  Files           62       62           
  Lines        13470    13508   +38     
========================================
+ Hits         12288    12324   +36     
- Misses        1182     1184    +2     

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