Add redundant_modulo_divisor lint

[Twil3akine]

Implements the % subset of #1324.

This adds redundant_modulo_divisor, which warns when the left-hand side of a remainder expression contains the divisor itself as an additive term.

Examples that lint:

(x + n + y) % n
(x + (n + y) + z) % (n + y)

This PR intentionally:

• handles only %, not /
• emits no suggestion
• handles only primitive integer operands
• requires at least three additive terms on the left-hand side
• ignores subtraction cases such as (x + n - y) % n
• does not search inside arbitrary additive subexpressions, to avoid false positives such as (x + (n + 1) + y) % n

Tested with:

cargo fmt --check
TESTNAME=redundant_modulo_divisor cargo uitest

changelog: [redundant_modulo_divisor]: add new lint for redundant additions of the modulo divisor

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[rustbot]

☔ The latest upstream changes (possibly #17552) made this pull request unmergeable. Please resolve the merge conflicts.