[feat] Comply with the semantic versioning specification

[vkarak]

This PR also adds the following:

• Expand deprecation message function to issue deprecation warnings in future releases.
• Old style of version specification is set to deprecate in 3.5.0

TODO:

• Update documentation of the @required_version decorator.

NOTE: The CI will fail due to an irrelevant reason. A separate PR will fix that (it's Gitlab CI lint failure)

[vkarak]

@teojgo The wheelvalidation works ;-) I will fix the PR.

[codecov-io]

Codecov Report

Merging #1761 (78a6739) into master (6838342) will increase coverage by 0.00%.
The diff coverage is 97.82%.

@@           Coverage Diff           @@
##           master    #1761   +/-   ##
=======================================
  Coverage   87.35%   87.36%           
=======================================
  Files          47       47           
  Lines        7792     7765   -27     
=======================================
- Hits         6807     6784   -23     
+ Misses        985      981    -4     

Impacted Files	Coverage Δ
reframe/utility/osext.py	84.71% <75.00%> (ø)
reframe/__init__.py	81.81% <100.00%> (ø)
reframe/core/decorators.py	97.08% <100.00%> (ø)
reframe/core/warnings.py	100.00% <100.00%> (ø)
reframe/frontend/runreport.py	92.55% <100.00%> (ø)
reframe/utility/versioning.py	96.77% <100.00%> (+3.08%)	⬆️

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