[BUG] The coalesced AVRO file may contain different sync markers if the sync marker varies in the avro files being coalesced.

[firestarman]

Describe the bug
The AVRO coalescing reading, introduced in #5306, will produce a big AVRO file with different sync markers when the sync marker varies in the original files. But one AVRO file should have the same sync marker in each sync block.

This bug exists because the reader simply concatenates the blocks from different files. We choose to do this is the implementation is quite simple for the quick start, and the cuDF AVRO reader ignores the sync markers for now.

Expected behavior
We should write the same sync marker into the coalesced AVRO file, no matter whether the original files have different sync markers.

[tgravescs]

so to clarify this isn't really a problem right now because CUDF ignores the sync markers right now, but we should clean it up in case they do, correct?

[firestarman]

so to clarify this isn't really a problem right now because CUDF ignores the sync markers right now, but we should clean it up in case they do, correct?

That's right.