test: consolidate esplora blocking and async test code

[notmandatory]

There should be a way to consolidate blocking and async tests and TestEnv (probably with macros as Alekos originally did).

Originally posted by @notmandatory in https://github.com/bitcoindevkit/bdk/pull/1110#discussion_r1316601369

[vladimirfomene]

@notmandatory do you think this can be labelled as a good first issue?

[ikeogu]

Good day team, can I contribute to this? Although I will need some briefing .

[notmandatory]

@ikeogu yes feel free to work on this, but first look over the code and post here or ask on discord if you have any questions before you get started.

[srikanth-iyengar]

@notmandatory I would like to contribute to this issue Correct me if I am wrong, Currently we have two separate tests for each blocking and async, and as you mention it is possible to have common tests covering both blocking and async ones

[notmandatory]

@srikanth-iyengar I think we need to figure out #1375 first, however that gets solved we should be able to use the same approach for this issue. What are your thoughts regarding the best way to consolidate async and blocking rust code?

[srikanth-iyengar]

I was thinking of something like

#[test_sync_async()]
fn test_both_sync_async() {
    let some_value = some_macro!( // this macro will decide which one to pick async or blocking 
         async { async_function().await },
        || sync_function()
    );
}

Will this be possible ? or we should go with synca