Conform models to Sendable

[jbelkins]

Describe the feature

Conform the model property types ByteStream and Document and the property wrapper @Indirect to Sendable.
Then conform all generated models (structs, unions, enums, intEnums) to Sendable.

No substantial change to these types should be needed to conform, except the @Indirect property wrapper which will require internal locking.

Use Case

This will aid customers in writing safe concurrent code in Swift 6 language mode.

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change