Add integration tests for electrum, esplora, bitcoind_rpc crates

[notmandatory]

Describe the enhancement

Basic blockchain integration tests need to be added to confirm scan and sync in different scenarios.

Use case

Example scan and sync test scenarios:

• single xkey or single key descriptors
• multisig xkey or single key descriptors
• multisig with mix of xkey and single key descriptors
• chain reorg
• synchronous or async

Additional context

Originally suggested by @danielabrozzoni on discord: https://discord.com/channels/753336465005608961/753367451319926827/1144280548802572319

[notmandatory]

To reduce duplicate code this should be done after #1113, with similar consolidated TestEnv for electrum and bitcoind_rpc crates.

[danielabrozzoni]

One of my biggest doubt for this is how to test examples. Running cargo test automatically checks that examples build, but we also need to test that they work correctly (otherwise we might have problems such as #1125 or #1151).

We might decide to duplicate the examples code into our tests, but then we need to make sure that the two stay up to date one with the other.

[nondiremanuel]

According to our previous discussion, for the moment I assign the beta release to both this and the #1113 issue and then if we can make it in time for alpha.3 they can be included

[notmandatory]

Blockchain crates have good test coverage, see #906. We should open new issues for specific scenarios that need more testing.