E2E: Generalize the specs

[gbarkhatov]

I think it's good enough at this stage.
A small improvement maybe you can think about is make this file more generic so that it's not specific to okx & keplr.
For example. we can create a map where left side is BBN wallet, and right side is BTC wallet. then each test case will loop through this mapping to check if all wallets are working as expected.
when we add new wallet, all we need to do is modify the config mapping

Originally posted by @jrwbabylonlab in #156 (comment)