Create Rule: Every visit must have associated timing

Guidance in section 1.3 of both the M11 Template (p22) and Tech Spec (p114) says (with bolding brackets round "trial" added by me - the Template text says "participants" instead of "trial participants" doesn't appear there in the Template text):
>The schedule of activities must capture the procedures that will be accomplished at each trial visit, and all contact with [trial] participants, for example, telephone contacts. This includes any tests that are used for eligibility, participant randomisation or stratification, or decisions on trial intervention discontinuation. **Allowable windows should be stated for all visits**.

Based on this, there should be 3 rules:
1. Every visit must have associated timing (this rule).
2. Every visit timing must have a window (#53).
3. Timing windows must be fully defined (#8)

Start by reviewing this issue with the related rules in issues #53 and #8, then locate the validation entry point and its existing tests. The payload names no files or tests, so confirm how visits and timing are represented before implementing the rule. Done means every visit is rejected when it has no associated timing.

Written by the indexing model from the issue text.