xmr: bp - gc (+14 squashed commits)

Squashed commits:
[4cf70d9] xmr: bp - gc
[42877b0] xmr: bp - minor memory optimization
[2c612e4] xmr: bp - use sc_inv_into
[d7e9dab] xmr: bp - KeyVEval fix
[1523f40] xmr: bp - blacked
[b264a65] xmr: bp - KeyVEval - caching current element, avoid allocations
[83ba7a6] xmr: bp - memory view optimized
[b517906] xmr: bp - gc() during inversion
[92d37c8] xmr: bp - gc.collect() after expensive inversion
[e7fad55] xmr: bp - hashing memory optimization
[4c27815] xmr: bp - deterministic masks optimization, prove_s1 optim
[cbf74a7] xmr: bp - detect which modular inversion is usable
[8ea1ec4] xmr: better memory tracing for bulletproofs
[2f4dd55] xmr: bulletproofs added