Support ephemeral addresses on processors

[Anilm3]

This PR introduces support for ephemeral addresses on processors, this includes:

• Expressions, allowing the partial or total evaluation of a processor.
• Mappings, allowing for the result of the processor to be ephemeral as well, so the same ephemeral address can be used to produce multiple variants of the same output address.

Remaining: unit tests...

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (80e31fd) 83.23% compared to head (02e31e8) 83.28%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #240      +/-   ##
==========================================
+ Coverage   83.23%   83.28%   +0.05%     
==========================================
  Files         106      106              
  Lines        4176     4177       +1     
  Branches     1914     1915       +1     
==========================================
+ Hits         3476     3479       +3     
  Misses        279      279              
+ Partials      421      419       -2     

Flag	Coverage Δ
waf_test_none	83.18% <100.00%> (+0.05%)	⬆️
waf_test_sse2	83.25% <100.00%> (+0.05%)	⬆️

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