[Improvement] Reduce number of dependencies (bech32, bs58)

[mahnunchik]

The number of dependencies can be reduced, making the package potentially more secure.

bech32 and bs58 can be removed in favor of @scure/base which is already in indirect dependencies list.

• bech32 https://github.com/paulmillr/scure-base?tab=readme-ov-file#bech32-bech32m-and-bitcoin
• base58 https://github.com/paulmillr/scure-base?tab=readme-ov-file#usage

[mahnunchik]

https://github.com/MystenLabs/sui/blob/main/sdk/bcs/src/hex.ts can be simplified as hex.decode and hex.encode from the same package @scure/base

[stefan-mysten]

Thanks @mahnunchik! I'll flag it to the right folks.

[hayes-mysten]

I'll add this to my list of things to work on for the SDK. We have some other high priority work going on right now, so I probably won't get to this right away, but this makes sense to me, and is something we should do in the not too distant future