compiler: Revamp linearization

[codecov[bot]]

Codecov Report

Attention: 26 lines in your changes are missing coverage. Please review.

Comparison is base (14ade37) 86.69% compared to head (df588c5) 86.67%.

Files	Patch %	Lines
devito/passes/iet/linearization.py	82.66%	20 Missing and 6 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2317 +/- ## ========================================== - Coverage 86.69% 86.67% -0.02% ========================================== Files 229 229 Lines 43043 43107 +64 Branches 7983 7996 +13 ========================================== + Hits 37318 37365 +47 - Misses 5034 5048 +14 - Partials 691 694 +3 ```

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