feat(osmomath): introduce more mutative math helpers for BigDec

[p0mvn]

Background

See the diff in this PR:
#6369

Notice TODOs marked with "TODO: (perf)"

We can optimize our math by creating mutative versions of the linked math helpers on BigDec that do not reallocate the internal buffer.

Suggested Design

For each individual helper, create a separate PR with the mutative versions that do not reallocate the internal buffer

Acceptance Criteria

• One PR per helper for BigDec defined on osmomath
• Unit tests
• All TODOs in refactor/test(CL): Stricter rounding behavior in CL math methods; unit tests at low price level #6369 are resolved

[p0mvn]

Related work: #6261

[hieuvubk]

@p0mvn Hi is anyone working on this?

[pysel]

hey @hieuvubk, I suppose it is free to pick up, since this has Help Wanted label! Thanks!