Remove the need for passing a location to parseAttribute/parseType.

Now that a proper parser is passed to these methods, there isn't a need to explicitly pass a source location. The source location can be recovered from the parser as necessary. This removes the need to explicitly decode an SMLoc in the case where we don't need to, which can be expensive.

This requires adding some basic nesting support to the parser for supporting nested parsers to allow for remapping source locations of the nested parsers to the top level parser for accurate diagnostics. This is due to the fact that the attribute and type parsers use different source buffers than the top level parser, as they may be represented in string form.

PiperOrigin-RevId: 278014858