[Epic] Remove unused DataStax-only code from the 4.x driver

[dkropachev]

Goal

Remove DataStax-only production code and tests that ScyllaDB neither uses nor exercises. This reduces the untested code shipped to users and the production, test, dependency, and compatibility surface the team must maintain.

Scope

• Remove Astra secure-connect-bundle support.
• Remove DataStax Insights monitoring.
• Remove DSE Graph, continuous paging, protocol extensions, authentication, types, metadata, and query-builder extensions.
• Remove the corresponding unit, integration, OSGi, CCM, build, native-image, Revapi, dependency, and documentation support.
• Preserve Scylla-specific features, including client routes/private endpoints.
• Preserve generic reactive CQL and mapper support; those classes are historically under com.datastax.dse but are not DSE-only.

Delivery

The work is tracked through this issue's native GitHub sub-issues. Each sub-issue gets a focused PR. If an unmerged child PR depends on another, cherry-pick only the exact required commit(s) and list those commits in the dependent PR description so rebasing remains straightforward.

Delivery order:

1. Independent first wave: Remove DataStax Astra secure-connect-bundle support #1026 / Remove unused DataStax Astra support #1034, Remove DataStax Insights monitoring #1027 / Remove unused DataStax Insights monitoring #1035, Remove DSE Graph support and TinkerPop integration #1028 / Remove unused DSE Graph support #1036, and Remove DSE authentication and proxy execution support #1030 / Remove unused DSE authentication support #1038.
2. After Graph removal: Remove DSE geometry and DateRange types #1029 / Remove unused DSE data types #1039, Remove DSE metadata, schema parsing, and query-builder extensions #1031 / Remove unused DSE metadata support #1040, and Remove DSE continuous paging and DSE protocol versions #1032 / Remove unused DSE protocol and continuous paging support #1041.
3. Final integration cleanup: Remove residual DSE compatibility, test infrastructure, and build wiring #1033 / Remove residual DSE compatibility and build wiring #1042.

Related existing work: #969 and #985 are superseded in scope by #1032; coordinate rather than duplicating their narrow negotiation change.

Completion criteria

• Every native sub-issue is merged or otherwise resolved.
• No DataStax-only runtime feature remains reachable.
• No tests or build configuration remain for removed features.
• The normal unit build passes.
• Relevant integration and packaging checks pass.
• Remaining com.datastax.* references are either public compatibility namespaces, attribution, or generic functionality intentionally retained.