Better errors for RDB parsing

[rohitpaulk]

In the RDB extension, since we rely on a third-party parser, our error messages aren't very helpful.

Example:

Error while parsing RDB file : unexpected EOF

Just like we do with RESPClient, we should write our own parser that can generate friendly error messages.

Thanks to @knusth for highlighting this!

[linear[bot]]

CC-1076 Better errors for RDB parsing

[rohitpaulk]

Actually wait, ignore this - we're only writing RDB files, user code handles reading. I thought it's the other way around when I created this