feat(abstract-utxo): update the keySignature verification network

[rushilbg]

BG-79423

[brandonblack]

Please update the commit messages in this PR to include an imperative mood statement of what changed, and why.

Example:

fix(abstract-utxo): always use bitcoin network for validating secondary key signatures

Key signatures are always generated with the bitcoin network because it is not always known which coin they will be used with. Without this change altcoin signatures would fail verification in some contexts.

For a rousing review of commit messages check out my recent brown bag talk :-D

[sachushaji]

Suggested change

	const userKeychain = await coin.keychains().create();
	const backupKeychain = await coin.keychains().create();
	const bitgoKeychain = await coin.keychains().create();
	const [ userKeychain, backupKeychain, bitgoKeychain] = await Promise.all([
	coin.keychains().create(),
	coin.keychains().create(),
	coin.keychains().create()
	]);

NIT: we can use promise.all instead of serially creating keychains

[OttoAllmendinger]

I don't believe we are making http requests here anyway though

[rushilbg]

These are synchronous operations, Promise.all won't speed them up.

Addressed

[OttoAllmendinger]

nits