cec7298: chore: fix cabal cache key in CI by including project hash (#143)

* chore: fix cabal cache key in CI by including project hash

the Github Actions configuration for the Cabal cache was not good
(despite it being the recommended configuration on the cache action
documentation; it’s just broken). The cache key is too fixed, so if
`ic-ref` changes, you still get a cache hit with the old store, and
still rebuild lots of dependendencies, but don’t push a new cache.

This tries to improve this, by including some of cabals configuration
files in the cache key.

(This is the same as https://github.com/dfinity/agent-js/pull/326)

* Update to path in ic-hs

Co-authored-by: Eric Swanson <[email protected]>