[Core] Fix isDouble flag not being set for 'type: number' without format

[berk-dilek]

Potentially fixes - #22624
When a schema has 'type: number' without an explicit 'format: double', the isDouble flag was not being set even though the dataType correctly resolves to Double. This caused Swift6 (and potentially other generators) to incorrectly add ParameterConvertible conformance to number enums.

The fix ensures isDouble is set to true for all number types that are not explicitly float, matching the behavior of the type mapping.

Affected methods:

• updateModelForNumber (for standalone enum models)
• updatePropertyForNumber (for inline enum properties)

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Summary by cubic

Fixed isDouble not being set for type: number without format. This aligns flags with Double type mapping and prevents Swift6 from adding ParameterConvertible to number enums.

• Bug Fixes
  • Set isDouble=true for non-float number schemas in updateModelForNumber and updatePropertyForNumber.
  • Covers both explicit format: double and no-format cases to keep generator behavior consistent.

^{Written for commit 349158b. Summary will update on new commits.}