Generalize callable (and newable) signatures

[kevinbarabash]

Call and constructor signatures should be generalized just like any other function signature.

[codecov]

Codecov Report

Merging #715 (2b1b03f) into main (4f0ee9b) will increase coverage by 0.53%.
The diff coverage is 90.27%.

@@            Coverage Diff             @@
##             main     #715      +/-   ##
==========================================
+ Coverage   85.34%   85.87%   +0.53%     
==========================================
  Files          61       61              
  Lines       11849    11843       -6     
==========================================
+ Hits        10112    10170      +58     
+ Misses       1737     1673      -64     

Files	Coverage Δ
crates/escalier_ast/src/type_ann.rs	100.00% <ø> (ø)
crates/escalier_hm/src/folder.rs	94.11% <100.00%> (+3.80%)	⬆️
crates/escalier_hm/src/types.rs	88.00% <100.00%> (+3.43%)	⬆️
crates/escalier_hm/src/unify.rs	86.56% <100.00%> (ø)
crates/escalier_interop/src/parse.rs	91.65% <100.00%> (+0.06%)	⬆️
crates/escalier_codegen/src/d_ts.rs	82.54% <0.00%> (-0.13%)	⬇️
crates/escalier_hm/src/infer.rs	94.27% <96.92%> (+2.56%)	⬆️
crates/escalier_hm/src/visitor.rs	43.36% <87.50%> (+6.77%)	⬆️
crates/escalier_parser/src/type_ann_parser.rs	95.53% <81.81%> (-0.46%)	⬇️
crates/escalier_interop/src/util.rs	88.95% <37.50%> (-1.91%)	⬇️