[tcgc] how can we rename an options bag's name?

```tsp
// By default, spread is spread: follow the TypeSpec blindly

// Make option bag generation the default for Java for the entire TypeSpec namespace.
// Use default strategy to pick up the name
@@optionBag(MyNamespace, "", "java")

// Use option bag for this operation, for rust. Generate name
@@optionBag(MyOperationn, "", "rust")

// Use option bag for this operation in Go, and name it explicitly
@@optionBag(MyOperation, "MyOperatitonOptions", "go")
```

Start with the @optionBag examples in the issue and trace the TypeSpec compiler code that handles option-bag names for namespaces and operations. Determine the intended behavior for an explicitly supplied name versus the default strategy, then confirm the expected result across the Java, Rust, and Go examples.

Written by the indexing model from the issue text.