## What changed?
Ignore unknown search attributes in visibility when encoding and
decoding.
## Why?
Unknown search attributes can only be possible on read/write path due to
a Predefined search attribute written by higher version server not
existing in lower version server constants.go that runs any Visibility
task.
This also fixes the read path discrepancy between ElasticSearch and SQL,
where ElasticSearch was dropping unknown search attribute field names,
but SQL was failing. Now, read path also ignores unknown search
attributes when reading instead of failing.
## How did you test it?
- [X] built
- [X] run locally and tested manually
- [X] covered by existing tests
- [X] added new unit test(s)
- [ ] added new functional test(s)
