re-add removed BignumPointer::bitLength()

[anonrig]

47c21db commit mistakenly removed a method added to BignumPointer and broke workerd.

Ref: 47c21db

cc @aduh95

[anonrig]

There are more methods removed with that commit. I'll readd them.

[aduh95]

Those are not in the upstream nodejs/node (or not anymore?), it's unclear what should be the course of action until nodejs/node#61613 (review) is resolved (i.e. should it be upstreamed in nodejs/node first? Or on the contrary, should we ask for thorough reviews here? Or let the two sources diverge?)

[anonrig]

Those are not in the upstream nodejs/node (or not anymore?), it's unclear what should be the course of action until nodejs/node#61613 (review) is resolved.

In the current state, it made a breaking change (and removed methods) without having a major version bump. I recommend re-adding them, and we can still continue on the discussion.