refactor(firehose-protos): use utility function for conversion error

[suchapalaver]

BACK-92

[linear]

BACK-92 Use a utility function for cleaner error handling conversion

Matter of preference, so feel free to push back. I just prefer the look of something like

pub fn unwrap_or_err<T, E>(option: Option<T>, error: E) -> Result<T, E> {
    option.ok_or(error)

// In some other code. Also, naming??
   let any = unwrap_or_err(response.block, ProtosError::NullBlock)?;

to

let any = response.block.ok_or(ProtosError::NullBlock)?;

I think it encapsulates how we handle errors. If this were to change, we wouldn't have to update 1000 things

[anirudh2]

Love this encapsulation!