Replace use of convertStringToHex/convertHexToString with stringToHex/hexToString

[mvadari]

convertStringToHex and convertHexToString are deprecated functions: https://github.com/XRPLF/xrpl.js/blob/main/packages/xrpl/src/utils/stringConversion.ts

These functions are really only still used in tests and snippets, so this is a pretty low priority issue. Just leaving it here as a reminder.

[Princeyadav05]

@mvadari can I give this one a try? I'm sure I would be able to tackle with your guidance.

[mvadari]

@mvadari can I give this one a try? I'm sure I would be able to tackle with your guidance.

Feel free, but I won't be able to provide any guidance.

[Princeyadav05]

@mvadari can I give this one a try? I'm sure I would be able to tackle with your guidance.

Feel free, but I won't be able to provide any guidance.

Sure, will give it a try.