Handle enum value order changes using LastContractView

[Copilot]

• Move BuildEnumValuesForBackCompatibility to TypeProvider as protected internal virtual
• Remove IsIntValueType check — applies to all fixed enum types
• Perform single Update call at end of ProcessTypeForBackCompatibility
• Revert string init value change in test data
• Remove explicit initialization values — let compiler auto-assign based on order
• Remove code comment from BuildEnumValuesForBackCompatibility
• Run eng/scripts/Generate.ps1

Original prompt

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This section details on the original issue you should resolve

<issue_title>LastContractView - handle eunm value order changes</issue_title>
<issue_description>Generator should be able to mitigate the breaking changes of enum order change to avoid custom code
such as https://github.com/Azure/azure-sdk-for-net/pull/53793/files#diff-2cb7c6853530fb07e8cf57678ea6093784b9d342b63785ad34a5b478e2962b4b</issue_description>

<agent_instructions>You are a .NET expert. Apply the fix for this but it should only be scoped to int enums. WRite proper unit tests exercising the scenario and also rerun ./eng/scripts/Generate.ps1 once you confirm all tests pass.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@jorgerangel-msft @live1206 - just to get clarity, in the example you linked the generated enum was

public enum KeyVaultCreateMode
    {
        /// <summary> recover. </summary>
        /// <summary> Recover. </summary>
        Recover,
        /// <summary> default. </summary>
        /// <summary> Default. </summary>
        Default,
    }

?</comment_new>
<comment_new>@live1206
@jorgerangel-msft Yes, the order of enum value changed from previous GA version.</comment_new>

• Fixes LastContractView - handle eunm value order changes #9438

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