Reduce number of REST calls during reads

[sfc-gh-mslot]

When reading a table from a REST catalog, we seem to make the same call several times.

table ice;
...
INFO:  making GET request to URL .../polaris/api/catalog/v1/MYDB/namespaces/PUBLIC/tables/Q1
...
INFO:  making GET request to URL .../polaris/api/catalog/v1/MYDB/namespaces/PUBLIC/tables/Q1
...
INFO:  making GET request to URL .../polaris/api/catalog/v1/MYDB/namespaces/PUBLIC/tables/Q1

Ideally, we would only make a single call. I suspect there's a planner + executor dimension, but not sure.

[sfc-gh-okalaci]

A prototype: #107

I think one dimension is the transaction isolation level. If we read once per-tx, we are in repeatable read mode. Currently, we fetch whenever we need, which is more like read-committed, but we read multiple times even within a query lifetime (which is wrong).

We should perhaps act based on the isolation level for the correctness.