[Bug]: http-client-java generator CodeNamer.getEnumMemberName doesn't handle "$100 Gift Card" as an enum

[er1c]

Describe the bug

Yes; it's a very very bad open api spec that has "$100 Gift Card" as an enum.

CodeNamer.getEnumMemberName("$100 Gift Card") generates: 100_GIFT_CARD which is an invalid java enum as it starts with a digit.

Reproduction

Assertions.assertFalse("100_GIFT_CARD".equals(CodeNamer.getEnumMemberName("$100 Gift Card")));

Will generate:

.... com.microsoft.typespec.http.client.generator.core.util.CodeNamerTests

org.opentest4j.AssertionFailedError: 
Expected :false
Actual   :true

Checklist

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• The provided reproduction is a minimal reproducible example of the bug.