Simplify Esplora::update_local_chain and add tests

[evanlinjin]

Fixes #1199

Description

After a second look at the update_local_chain implementations, it was clear that they were over complicated. This PR simplifies the EsploraExt::update_local_chain method(s) of the bdk_esplora crate and adds a whole bunch of tests.

Notes to the reviewers

The description of #1199 is very brief, however @danielabrozzoni mentioned about potentially-problematic logic with ASSUME_FINAL_DEPTH. The logic was indeed convoluted and it did not need to be that way. This PR removes the need for ASSUME_FINAL_DEPTH.

Changelog notice

Fixed

• Simplified EsploraExt::update_local_chain logic.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

Bugfixes:

* [ ] This pull request breaks the existing API
* [ ] I've added tests to reproduce the issue which are now passing (there are now lots of tests though)

• I'm linking the issue being fixed by this PR

[evanlinjin]

@notmandatory this doesn't really change the API

[LLFourn]

Concept ACK. One thing looks like it needs to be updated.

[LLFourn]

I found some more things that could be simplified as part of this.

[LLFourn]

self-ACK: 216648b

Pushed a comment and docs better explaining what @evanlinjin was trying to explain to me here: #1267 (comment)

[evanlinjin]

ACK 216648b

Thank you @LLFourn for the improved docs.

[danielabrozzoni]

A few nits, otherwise LGTM

[danielabrozzoni]

What if no point of agreement is found? Is this possible?

[evanlinjin]

This should never happen because the genesis block must connect! However, let's say hypothetically, the genesis doesn't connect (because the wallet and esplora are on different networks), the update formed will try replace the genesis, resulting in the local_chain::MissingGenesisError which is the error that we want!

[notmandatory]

Found a couple typos that should be fixed.

[notmandatory]

To fix CI in cont_integration.yml try replacing:

          cargo update -p zip --precise "0.6.2"

with:

          cargo update -p zstd-sys --precise "2.0.8+zstd.1.5.5"`

[evanlinjin]

ACK c5afbaa

Thank you @notmandatory for spotting the typos and fixing the CI!

[notmandatory]

utACK c5afbaa