Reorganize code to keep code as IRCode slightly longer (#39885)
This moved the primary place where IRCode gets converted into CodeInfo
into the transform_result_for_cache call, which is a sensible place for
it to be since the primary reason we need to convert back to IRCode is
to make it acceptable for storing in the global cache. The reason we
might want to not perform the conversion, is that the conversion is
slightly lossy, because it drops stmtinfo. However, in Cthulhu, I would
like to keep the statement info around such that Cthulhu can present
it to the user, even in optimized code (i.e. where inlining decided
not to inline, I would still like Cthulhu to be able to introspect
inference's original annotations). This change makes that possible.
In an ideal world, we wouldn't have to do this at all for uncached
code, but of course both code_typed and typeinf_ext do look at the
code, even if it is uncached. Unfortunately, at the moment we don't
really have a good way to indicate whether or not the code will
be looked at, so there is a fallback path that always does the
conversion if we decided not to do the caching. Some future
refactoring can save some additional time here.
