docs: deprecate Java Driver 3.x and announce maintenance mode

[nikagra]

DRIVER-854: Deprecating Java Driver 3.x

This PR marks Java Driver 3.x as deprecated and announces maintenance mode, part of the DRIVER-483 epic (tracked as DRIVER-854).

Changes

File	Change
README.md	Added deprecation notice at top with link to 4.x; updated version references from 3.11.5.0 to 3.11.5.15
docs/source/conf.py	Added all 3.x doc branches to DEPRECATED_VERSIONS so the Sphinx docs site marks them as deprecated in the version picker
docs/source/_templates/notice.html	Added deprecation warning banner above the existing license notice
changelog/README.md	Added deprecation announcement entry

What this means

• Java Driver 3.x enters maintenance mode -- only critical bug fixes will be accepted
• Users are directed to migrate to Java Driver 4.x
• The documentation site will display deprecation indicators for all 3.x versions

Remaining DRIVER-483 tasks (out of scope for this PR)

• Compile inventory of internal tools using java-driver 3.x
• Compile inventory of external tools and integrations using java-driver 3.x
• Publish deprecation announcement in internal and external documentation portals
• Prepare and publish a performance comparison blog post

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[annastuchlik]

@mikliapko When this PR is merged and the information is published with the new driver release, we need to update the generic Drivers page and driver support to indicate that 3.x is deprecated.
https://docs.scylladb.com/stable/drivers/cql-drivers.html
https://docs.scylladb.com/stable/versioning/driver-support.html

Sources at https://github.com/scylladb/scylladb-docs-homepage/tree/main/docs

[mikliapko]

@mikliapko When this PR is merged and the information is published with the new driver release, we need to update the generic Drivers page and driver support to indicate that 3.x is deprecated. https://docs.scylladb.com/stable/drivers/cql-drivers.html https://docs.scylladb.com/stable/versioning/driver-support.html

Sources at https://github.com/scylladb/scylladb-docs-homepage/tree/main/docs

I suppose it's @nikagra who should have been tagged :)

[annastuchlik]

I suppose it's @nikagra who should have been tagged :)

True, sorry!