### What changes were proposed in this pull request?
When creating a record writer in an AvroDeserializer, or creating a struct converter in an AvroSerializer, look up Avro fields using a map rather than scanning the entire list of Avro fields.
### Why are the changes needed?
A query against an Avro table can be quite slow when all are true:
* There are many columns in the Avro file
* The query contains a wide projection
* There are many splits in the input
* Some of the splits are read serially (e.g., less executors than there are tasks)
A write to an Avro table can be quite slow when all are true:
* There are many columns in the new rows
* The operation is creating many files
For example, a single-threaded query against a 6000 column Avro data set with 50K rows and 20 files takes less than a minute with Spark 3.0.1 but over 7 minutes with Spark 3.2.0-SNAPSHOT.
This PR restores the faster time.
For the 1000 column read benchmark:
Before patch: 108447 ms
After patch: 35925 ms
percent improvement: 66%
For the 1000 column write benchmark:
Before patch: 123307
After patch: 42313
percent improvement: 65%
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
* Ran existing unit tests
* Added new unit tests
* Added new benchmarks
Closes#32969 from bersprockets/SPARK-35817.
Authored-by: Bruce Robbins <bersprockets@gmail.com>
Signed-off-by: Gengliang Wang <gengliang@apache.org>
66d5a0049a