fix: canvas custom comparison not applying

[AdityaHegde]

Canvas custom comparison option was non functional.

1. Min/max dates were swapped, leading to invalid interval.
2. Custom range was considered as new rill time and ignored in comparison time.

Note that this is a minimal set of changes. There is a massive refactor coming to time controls that will add tests etc.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

[nishantmonu51]

isNewRillTimeFormat now returns false for new-syntax absolute ranges (parser.ts:17, RillTime.ts:49)

2024-01-01 to 2024-02-01, 2024-01-01/2024-02-01 and 2024-01-01,2024-02-01 all parse to RillIsoInterval — new format by the name's own reading — yet now report false. The one caller (comparisons/index.ts:325) is really asking "must I resolve this expression instead of computing the range here", which is not the same question, and a later reader has no way to tell absolute ranges are excluded too.

isAbsolute duplicates isAbsoluteTime() (RillTime.ts:49, RillTime.ts:103)

Same instanceof RillIsoInterval check, now in two places to keep in sync. Calling parser.isAbsoluteTime() from isNewRillTimeFormat drops the field; renaming it to state what it means (isRillTimeExpression) makes the call site self-explanatory.

Test (comparisons/index.spec.ts:124)

A case for "2024-01-01T00:00:00.000Z,2024-02-01T00:00:00.000Z" in getComparisonIntervalTests pins this regression. The adjacent invalidComparisionTests covers the new-syntax rejections but not the absolute-range acceptance.