Refactored RPC handling

[suhasasumukh]

Changes made:

• enhanced float point precision, variable naming, annotation, function name

[GitBolt]

Sorry but this PR improves nothing either.

• Adding type str to message in init of RPCRequestError is a minor thing and worth it, sure, but does it need a PR? No.
• You rewrote the truncate_float function to be more readable, but it is less performant. There isn't really much difference and readability is not a big concern for functions defined with SDK for SDK users, they just have to use it.
• There is absolutely not reason to modify lamport_to_sol function to change the value using division. In fact, division is slightly less performant than multiplication
• Why would you remove string input option from verify_signature function and only allow bytes for message? Most beginners are familiar with entering a string for message, a public key and signature to get the result. We can convert it to bytes for them, like it was being done right now. Why remove?

Please make meaningful pull requests. Most of your pull requests have been closed due to providing non-essential value and sometimes instead making the code worse. This is not how you contribute to open source.