feat(rpc): add getrawtransaction

[conradoplg]

Motivation

We need the getrawtransaction RPC in order to support lightwalletd.

Specifications

Designs

Solution

• Change transaction-fetching functions to also return the block height they're in (this will likely be refactored in the upcoming database changes)
• Add getrawtransaction

Based on #3907

Closes #3145

Review

It's mostly complete, it's a draft just because I want to add more tests. But I'd welcome a initial review on the implementation.

Reviewer Checklist

• Code implements Specs and Designs
• Tests for Expected Behaviour
• Tests for Errors

Follow Up Work

[oxarbitrage]

I didnt checked eveything yet but leaving some feedback. All minor stuff.

[teor2345]

This is completely optional, but I prefer try_into over as, because it catches bugs earlier.

[conradoplg]

Thanks for the comments! I've rebased this and addressed them, but I'm still working on tests

[conradoplg]

This is now ready for final review.

I couldn't come up with new tests other than a couple of proptests for failure cases in 1c3c081, and integration tests seem to require cached state (I thought of spinning both serves and getting a tx from e.g. the second block, but that seems redundant with the cached state test). I also tested manually with curl, e.g.

curl -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"getrawtransaction","params":["30391bc7873e593e4eb99b373a184666995e0cbc6e303d0aa79e8221941fb3eb",1],"id":123}' 127.0.0.1:28232

[teor2345]

Looks good to me, I'm happy for @oxarbitrage to resolve the discussions we both commented on.

[oxarbitrage]

Looks good.

[teor2345]

@Mergifyio update

[mergify]

update

✅ Branch has been successfully updated