Prefix all unconstrained oracle calls with `unsafe_`

[benesjan]

Note: Might not make sense to tackle given that we might get a real language support soon (see issue).

It's currently basically impossible to figure out what function results need constraining and what not. This is big danger so make sense to just prefix every function which doesn't constrain oracle results with unsafe_

Look for "TODO(#6543)" in the codebase.

[nventuro]

Closing in favor of unsafe blocks, as introduced in #8232.