Fixes for short form function locations

[c42f]

• Bump trivia after = so we see the correct line for functions in multiple-assignments like let f(x) =\ng(x)=1\nend
• Fixes for insertion of these line numbers on the right hand side
• Remove special case avoiding inserting short form function location when in for loop iteration spec; allow this in Expr comparison instead.

Part of #270

[codecov[bot]]

Codecov Report

Merging #284 (1cb6843) into main (b5971af) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #284   +/-   ##
=======================================
  Coverage   96.69%   96.69%           
=======================================
  Files          14       14           
  Lines        4027     4029    +2     
=======================================
+ Hits         3894     3896    +2     
  Misses        133      133           

Impacted Files	Coverage Δ
src/expr.jl	100.00% <100.00%> (ø)
src/parser.jl	98.25% <100.00%> (+<0.01%)	:arrow_up: