feat: add icrc3_get_transactions

[MarioDfinity]

1. add the icrc3_get_transactions endpoint following the ICRC-3 standard
2. add tests against the endpoint that cover the single range query case

[THLO]

This comment is a bit confusing, at least to me.
Effectively, you are extracting the actual block because it has the timestamp set, which you need to compute the correct hash, right?

[MarioDfinity]

Yes. The timestamp cannot be computed so I need to fetch it. I could just change the timestamp field of the block instead to make it more clear.

[THLO]

Updating the comment to make it clearer or changing the timestamp field, either way works for me. You choose! :-)

[MarioDfinity]

I've done both with c65cad0. I set the timestamp and I changed the description to explain why I do it. Is it better?

[THLO]

Same here.

[THLO]

The PR is missing a description. Could you add one, please?
It is especially useful to describe what the PR covers and what it does not cover (such as additional testing that will follow later).

[MarioDfinity]

The PR is missing a description. Could you add one, please? It is especially useful to describe what the PR covers and what it does not cover (such as additional testing that will follow later).

Done!