Make Ptr hashing functions pure

[arthurpaulino]

Pointer hashing functions used to throw errors when the data needed for hashing wouldn't be found in the store. However, this indicates a malformed store, meaning that interning must have gone wrong somewhere else. So a straightforward panic is more adequate.

This simplifies a lot of calls to Store::hash_ptr, which were being unwrapd or expectd in many cases anyway.

[huitseeker]

Thanks for the cleanup!

[arthurpaulino]

!benchmark
!gpu-benchmark

[github-actions]

Benchmark for ef9a71f

Click to view benchmark

Test	Base	PR	%
LEM Prove/Fibonacci-rc=100/num-100/a791459ea98ed014859282c673e2f3ad4505c98e-2023-10-31	12.2±0.15s	N/A	N/A
LEM Prove/Fibonacci-rc=100/num-100/ef9a71f1954ae8b2e339782896cd821b2ec5353e-2023-10-31	12.3±0.11s	N/A	N/A
LEM Prove/Fibonacci-rc=100/num-200/a791459ea98ed014859282c673e2f3ad4505c98e-2023-10-31	24.4±0.85s	N/A	N/A
LEM Prove/Fibonacci-rc=100/num-200/ef9a71f1954ae8b2e339782896cd821b2ec5353e-2023-10-31	24.2±0.19s	N/A	N/A