Clash potentially unreliable on GHC 9.10 on 32-bit hosts

[christiaanb]

Once #2758 is merged, Clash can be built with GHC 9.10. However, we punted on switching the internal implementation of Unique from Int to Word64; which GHC 9.10 did do. As a result, compiling to HDL using a Clash compiler built against GHC 9.10 might become unreliable on 32-bit platforms.

We should do two things:

1. When we update the GHC compatibility matrix in the README, we should highlight that 32-bit platforms are "unsupported" for GHC 9.10
2. Upgrade our Uniques to Word64 bit as well. Though I want to make this part of an update where we rethink our Unique story, which is why I punted on it for the GHC 9.10 upgrade.