Doc: Create messaging for SNMP integration to go in release notes

[karenzone]

Add content to pre-announce the SNMP-integration (at Technical Preview for 8.14.0) and help set user expectations around upcoming changes.

Release notes messaging:

• main
• 8.14: Release notes for 8.14.0 #16155

Breaking changes:

• main

[karenzone]

Starter content

[[featured-8-14-0]]
==== Announcing the new SNMP integration plugin (Technical Preview)

The new {logstash-ref}/plugins-integrations-snmp.html#plugins-integrations-snmp-migration[logstash-integration-snmp] plugin is now available in Technical Preview, and can be installed on {ls} 8.13.

experimental[]

The logstash-integration-snmp plugin combines our
classic logstash-input-snmp and logstash-input-snmptrap plugins into a single Ruby gem at v4.0.0.
Current 1.x versions of the input-snmp plugin are bundled with {ls} by default, and will soon be replaced by the 4.0.0+ version contained in this new integration.

If you want to try the new integration-snmp plugin while it is in Technical Preview, run bin/logstash-plugin install logstash-integration-snmp.

IMPORTANT: Before you install the new integration, be aware of {logstash-ref}/plugins-integrations-snmp.html#plugins-integrations-snmp-migration[behavioral and mapping differences] between current stand-alone plugins and the new versions included in integration-snmp.