Remove experimentalIsUnifiedHost flag from DatabricksConfig

[hectorcast-db]

Summary

Ports databricks/databricks-sdk-go#1641 and databricks/databricks-sdk-py#1358 to the Java SDK.

Drops the experimentalIsUnifiedHost field and the DATABRICKS_EXPERIMENTAL_IS_UNIFIED_HOST environment variable from DatabricksConfig. The flag was never read in production:

• DatabricksConfig.getHostType() derives the host type purely from the URL pattern.
• Unified-host metadata fields (accountId, workspaceId, discoveryUrl) are auto-resolved via /.well-known/databricks-config during config.resolve().

No production path referenced the flag, and no tests set it (confirmed via grep across the repo).

Breaking change

This is a compile-time breaking change. Downstream callers that were setting the flag should drop those calls:

// Remove any usage of:
config.setExperimentalIsUnifiedHost(true);
config.getExperimentalIsUnifiedHost();

// Remove the env var from deployment configs:
DATABRICKS_EXPERIMENTAL_IS_UNIFIED_HOST

No user-facing replacement is needed — unified host detection is automatic.

Scope vs. the Go/Python PRs

Change	Applies to Java?
Remove Experimental_IsUnifiedHost field + env var	✅ ported here
Remove ErrWorkspaceIDInAccountClient (Go only)	❌ no equivalent in Java
README docs for unified host / default auth flow	➖ skipped — Java's README does not cover the same sections; documentation can follow in a separate PR if desired

Test plan

• mvn compile clean
• mvn test — 1187 tests pass, no regressions
• Spotless clean
• No remaining references to experimentalIsUnifiedHost / EXPERIMENTAL_IS_UNIFIED_HOST in the repo (grep clean)

This pull request was AI-assisted by Isaac.

[github-actions]

If integration tests don't run automatically, an authorized user can run them manually by following the instructions below:

Trigger:
go/deco-tests-run/sdk-java

Inputs:

• PR number: 773
• Commit SHA: 1ffda2c7cd35648cffa45784893bc74040b07d8d

Checks will be approved automatically on success.