regression in gc safety of debuginfo

[vtjnash]

If a codeinst is not in a cache, it is not legal to call the code generation method, as this method pushes the object into the global debuginfo / JIT structs and later returns those, which can result in GC use-after free bugs

Originally posted by @vtjnash in #53219 (comment)

Posting as a new issue, since the original PR is already merged, so that this doesn't get lost

[aviatesk]

Fixed in #54816 (IIUC)