avro

AVRO-3642: [RUST] Fix GenericSingleObjectReader::read_value for non-exhaustive reads (#1914)

* AVRO-3642: Add test to reader.rs to expose bug on non-exhaustive read

* AVRO-3642: Call read_exact in GenericSingleObjectReader when reading header

* AVRO-3642: Correct name reader::tests::avro_3642_test_single_object_reader_incomplete_reads

Co-authored-by: Martin Grigorov <martin-g@users.noreply.github.com>

* AVRO-3642: In test, initialize vector with two-byte marker

Co-authored-by: Martin Grigorov <martin-g@users.noreply.github.com>