Currently, each record header is decoded at least twice: once to
determine the record size within the read buffer (in order to construct
the `ImmutableRecord` instance), and again later when decoding the
record for comparison. This redundant decoding can have a noticeable
negative impact on performance when records are wide (eg. contain
multiple columns).
This update modifies the (de)serialization format for sorted chunk files
by prepending a record size varint to each record payload. As a result,
only a single varint needs to be decoded to determine the record size,
eliminating the need to decode the full record header during reads.
Closes#2176
9936748132