Revert "Core: Use encoding/decoding methods for namespaces and deprecate Splitter/Joiner"

[nastra]

Reverts #10858

I'll revert this one for now and do a proper fix for 1.8.0

[bryanck]

I'm not convinced we need to revert this. In my test env I have Trino 465 + 1.7 with nested namespaces enabled, connecting to an Iceberg 1.6 REST catalog. I'm seeing the same error in the REST catalog: Unhandled error: ErrorResponse(code=404, type=NoSuchNamespaceException, message=Namespace does not exist: bck%1Fdb1) whether Trino is using 1.7.0 or this branch. Perhaps we can assume that if you have nested namespaces enabled in Trino you need a REST catalog with 1.7?

[nastra]

@bryanck the issue is that the 1.7 client sends the query param (where the nested namespace is encoded) using %1F but the 1.6 catalog expects the non-UTF-8 encoded character \u001f. Basically Iceberg 1.6 prior to #10858 used RestUtil.encodeNamespace() / RestUtil.decodeNamespace() only for paths and used \u001f directly with a Splitter/Joiner for the query param on the client and the server, which effectively causes the issue.
#10858 was mainly introduced for #10877, so I'll revisit the approach but in the meantime it's probably the safest to just revert.

[bryanck]

I retested this and this does resolve the issue (I tested the wrong Trino build previously).

[nastra]

thanks for reviewing and testing this @bryanck

[mayankvadariya]

Related issue #11539