inference: fixes cache lookup with extended lattice elements
The previous local cache lookup system wasn't working well for caches
with extended lattice elements that are transformed from the caller
context to the callee context by `matching_cache_argtypes`. To address
this, the current commit moves the call to `matching_cache_argtypes`
right before `cache_lookup`, instead of within the `InferenceResult`
constructor.
Note that this adjustment leads to `given_argtypes` being allocated even
when there's a cache hit, potentially affecting performance negatively.
I'm looking to further optimize `matching_cache_argtypes` in an upcoming
commit.
