fix($parse): make equality and relational operators left-associative

This fixes an associativity issue in expressions that use multiple
equality or relational operators back to back without grouping.

Previously, these expressions were right-associative, which may
cause confusion for users who expect them to behave identically
to JavaScript expressions.

An expression like "a === b === c" was evaluated as "a === (b === c)".
Now it is evaluated as it is in JavaScript: "(a === b) === c".