ICU-22940 MF2 ICU4C: Update for bidi support

[catamorphism]

The tests in this PR are also included in a PR against the MF2 spec. However, some editing will have to occur unless https://github.com/unicode-org/icu/pull/3198 (matching on variables instead of expressions) lands before then. There was a spec change to the syntax of .match constructs, and some of the tests include .match constructs.

Checklist

• [x] Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22940
• [x] Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• [x] Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• [x] Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• [x] Issue accepted (done by Technical Committee after discussion)
• [x] Tests included, if applicable
• [x] API docs and/or User Guide docs changed or added, if applicable