Search & Remove reductant api's in `utill.rs`

[KnowWhoami]

In the utill.rs file, there are several functions that perform tasks for which APIs already exist in the dependency libraries.

For example https://github.com/citadel-tech/coinswap/blob/691c937454ccf1c2a182ef0aca1d514b7f74606d/src/utill.rs#L465

• This function converts a network string into a Network struct. However, we don't need to create a separate API for this functionality, as it can be accomplished using the existing Network::from_str() method from rust-bitcoin.

• Thus we have to find all such functions and remove them and directly call corresponding built-in apis.

[KnowWhoami]

• For BDK related api's -> do not remove those functions now as that must be done while integrating our wallet with BDK.
• Just raise another issue for them.