Implement ElectrumExt for all that implements ElectrumApi

[evanlinjin]

Description

Implement ElectrumExt for all that implements ElectrumApi.

I realized this while looking into #1171.

bdk/crates/electrum/tests/test_electrum.rs

Lines 54 to 55 in 2196685

	let env = TestEnv::new()?;
	let client = electrum_client::Client::new(env.electrsd.electrum_url.as_str())?;

Line 55 here should not be necessary.

Changelog notice

• Changed to implement ElectrumExt for all that implements ElectrumApi.

Checklists

All Submissions:

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

[notmandatory]

ACK ce8c617