fix: #446 Weekview does reflect changes to startHour and endHour.

[bsutton]

Description

The week view doesn't reflect changes to startHour or endHour when it rebuilds.

Move move both of these values into the InternalWeekView state and update the state when the widget changes.

Checklist

• [ x] The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• [ x] I have followed the Contributor Guide when preparing my PR.
• [ x] I have updated/added tests for ALL new/updated/fixed functionality.
• [ x] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [ x] I have updated/added relevant examples in examples or docs.

Breaking Change?

None

Migration instructions

Not required.

• Yes, this PR is a breaking change.
• [x ] No, this PR is not a breaking change.

Related Issues

Closes #446