Define a property of model with default value returns error in autorest & OAS3 emitter

[lirenhe]

Describe the bug

model Test {

user: {
name: string;
} = #{ name: "System" };
}
returns error of 'Invalid type 'ObjectValue' for a default value' in cadl playground.

Reproduction

https://azure.github.io/typespec-azure/playground?c=Cgptb2RlbCBUZXN0IHsKCiAgdXNlcjogewogICAgbmFtZTogc3RyaW5nOwogIH0gPSAje8cXIlN5c3RlbSIgfTsKfQo%3D&e=%40azure-tools%2Ftypespec-autorest&options=%7B%22linterRuleSet%22%3A%7B%22extends%22%3A%5B%22%40azure-tools%2Ftypespec-azure-rulesets%2Fdata-plane%22%5D%7D%7D

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[timotheeguerin]

Same as #4193 this is more of a feature request where we have never supported non primitive default values