Enhance performance of rz_bv_copy_nbits and rz_bv_set_range

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Is your feature request related to a problem? Please describe.

Performance could be better and we save energy which would make us better humans.

Describe the solution you'd like

Both functions do something like this:

for (ut32 i = 0; i < nbit; ++i) {
   bool c = rz_bv_get(src, src_start_pos + i); // Not in case of rz_bv_set_range()
   rz_bv_set(dst, dst_start_pos + i, c);
}

At least if we deal with small bit vectors (<= 64bit) we could do this with shift, AND + OR.
This would save a bunch of calls and other shifts and ORs.

For larger bit vectors we could check if the range is large enough (e.g. 8 bits or more).
Then set the first bits until the rest of them is aligned to a multiple of a byte (for RzBitVector->large_a) and assign the rest of them via memcopy.

Describe alternatives you've considered

None really.

Additional context

This would give us quite some computation back. In my use case this loop consumes around 2.3%.
I also think this is a required improvement before we merge resource intensive analysis algorithms based on it.

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Possible implementation: https://graphics.stanford.edu/~seander/bithacks.html#MaskedMerge.
Simple for ut64 values, would need to be generalized to everything >64bits.