feat: Support generic exec

[jawoznia]

No description provided.

[codecov]

Codecov Report

Merging #242 (4742385) into feat/generics_support (3d78b45) will decrease coverage by 1.93%.
Report is 3 commits behind head on feat/generics_support.
The diff coverage is 95.19%.

@@                    Coverage Diff                    @@
##           feat/generics_support     #242      +/-   ##
=========================================================
- Coverage                  87.83%   85.91%   -1.93%     
=========================================================
  Files                         25       24       -1     
  Lines                       1595     1654      +59     
=========================================================
+ Hits                        1401     1421      +20     
- Misses                       194      233      +39     

Files	Coverage Δ
sylvia-derive/src/input.rs	92.98% <100.00%> (-2.26%)	⬇️
sylvia-derive/src/interfaces.rs	87.87% <100.00%> (-2.78%)	⬇️
sylvia-derive/src/multitest.rs	96.29% <100.00%> (+2.12%)	⬆️
sylvia/src/types.rs	80.00% <ø> (ø)
sylvia-derive/src/parser.rs	81.64% <87.50%> (-1.05%)	⬇️
sylvia-derive/src/message.rs	82.73% <93.46%> (-0.84%)	⬇️

... and 2 files with indirect coverage changes

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[hashedone]

Looks mostly good to me with one relevant comment - I thnk it still can be a CT check with a minimal change.