Refactor precedence handling in parser

[kevinbarabash]

• add parse_infix() and parse_prefix() methods to expr_parser.rs
• normalize precedence, handle Right associativity, prevent assignment chaining
• update type_ann_parser to mimic changes to expr_parser

[codecov[bot]]

Codecov Report

Merging #710 (3b10bea) into main (f3eabc0) will increase coverage by 0.06%. The diff coverage is 98.18%.

@@            Coverage Diff             @@
##             main     #710      +/-   ##
==========================================
+ Coverage   85.24%   85.31%   +0.06%     
==========================================
  Files          61       61              
  Lines       11705    11730      +25     
==========================================
+ Hits         9978    10007      +29     
+ Misses       1727     1723       -4     

Files	Coverage Δ
crates/escalier_parser/src/precedence.rs	96.42% <96.15%> (-3.58%)	:arrow_down:
crates/escalier_parser/src/type_ann_parser.rs	95.98% <98.75%> (+0.44%)	:arrow_up:
crates/escalier_parser/src/expr_parser.rs	97.18% <98.24%> (+0.16%)	:arrow_up:

... and 2 files with indirect coverage changes