feat/private-input: Unconstrained memory init

[naure]

Issues #614 and #607

Initialize memory with unconstrained prover hints.

• It is practically identical to the zero-init circuit; just without the zero-init part.
• The address range must be contiguous, but its size is dynamic.
• The u32 range check is already done by the LOAD and STORE circuits.

e2e integration will be done in another PR. Need #608 to configure the address space.