Allow commitInfo's operationParameters to have non-string values

[zachschuermann]

For existing tables in the wild we've seen some with "operationParameters":{"version":10,"timestamp":null}. This breaks reads with the following error:

Error: Arrow(JsonError("whilst decoding field 'commitInfo': whilst decoding field 'operationParameters': expected string got 10"))

Despite commitInfo allowing arbitrary JSON (unless constrained by in-commit timestamps), we attempt to prescribe structure when reading. This should almost never fail but due to arrow json reading it errors on attempting to read int 10 as a String.

We likely need to come up with a way to allow deserializing arbitrary JSON in operationParameters? How can we represent that with our existing Schema system?

[zachschuermann]

related: delta-io/delta#2419