feat(rpc): add z_validateaddress endpoint

[nachog00]

Motivation

#219.

Solution

Implement z_validateaddress.

• The PR name is suitable for the release notes.
• The solution is tested.
• The documentation is up to date.

[nachog00]

This approach is outdated. We are PRing into zebra to have their methods exposed (both for this and validateaddreess).

I'll hold off until ZcashFoundation/zebra#9658 get's reviewed to PR the analogous changes for this RPC in zebra, that way we avoid back and forward with placing of the refactored function. This PR will be redone with that pattern too.

[zancas]

Is this still planned for Zaino.. or is the functionality going to be elsewhere... let's figure this out and, if correct, close this PR. Or else say why not.

[ala-mode]

I'll hold off until ZcashFoundation/zebra#9658 get's reviewed to PR the analogous changes for this RPC in zebra...

Just as a heads up, this got merged into zebra ~5 days ago.

[zancas]

One more little thing that seems off.

@fluidvanadium What?

[fluidvanadium]

One more little thing that seems off.

@fluidvanadium What?

That was error handling. Now the only issue is partial sapling keys

[pacu]

utACK! (modulo fixing the failing test)

[zancas]

@nachog00 what's the status of this work. I thought that it was quite close to completion, but now I see merge conflicts.

Can you update it and resolve the conflicts, or close it as won't merge?

[fluidvanadium]

LGTM