receiver/postgresql: bump PostgreSQL minimal supported version to latest official supported

[kevinnoel-be]

Component(s)

receiver/postgresql

Is your feature request related to a problem? Please describe.

I see that this receiver is marked as supporting PG 9.6+ in the README. Do we still want to keep this much backwards compatibility given that this is quite an old, and unsupported for 2+ years, version now (list of PG versions here). It seems that the latest supported version is PG 12 with still ~9 months of support and we should maybe align on this?
This can make improvements, using more recent features (a bit?) harder or use less maintained/out-of-date modules versions (e.g. #30831)

Describe the solution you'd like

Update the prerequisites requirements for using this receiver (+ integration tests) to the latest officially supported PostgreSQL version

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• receiver/postgresql: @djaglowski

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[djaglowski]

I'm in support of this. Let's leave the issue open for a couple weeks so others can weigh in.

[github-actions]

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Pinging code owners:

• receiver/postgresql: @djaglowski

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[djaglowski]

No one has argued otherwise. I suggest we initially add a deprecation warning to the changelog, then remove in a subsequent version.