Prepare static-alloc for 0.3.0

[197g]

Fixing a bunch of inconsistencies here:

• More soundness precautions around coercing into the slice, so the synchronous variant in particular does not implement Deref but rather an explicit method. (It's not allocated).
• Far fewer monomorphization. The bulk implementation does not live on Bump<T> but a shared proxy for the raw memory interaction (so even our code only uses T for its layout and turning that into a runtime value asap).
• A slice variant for the Sync Bump.