Motivation:

It was noticed that many of the commands are cumbersome to use with boilerplate type casting for each use that can be simplified within the library
by doing type conversion before returning the value to an end user.

Modifications:

Many APIs that return a `RESPValue` now have overloads to provide a `RESPValueConvertible` type that the value will be turned into before being returned.

For a few APIs that returned `RESPValue`, they did so as an Optional. Those APIs have been changed to always provide a `RESPValue` and return `.null` in cases where `nil` was returned.

In addition, the `@inlinable` attribute has been removed from any non-generic command API.

Result:

Developers should have less code boilerplate for turning values from `RESPValue` to their desired type with many commands.