ICU-23209 Don't load standard patterns by default in DTPG

[sffc]

This makes DTPG consider only availableFormats instead of standard patterns.

Checklist

• [x] Required: Issue filed: ICU-23209
• [x] Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• [x] Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• [ ] Issue accepted (done by Technical Committee after discussion)
• [ ] Tests included, if applicable
• [ ] API docs and/or User Guide docs changed or added, if applicable

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Notice: the branch changed across the force-push!

• icu4j/main/core/src/test/java/com/ibm/icu/dev/test/format/DateTimeGeneratorTest.java is different

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