[postgres] Fix unicode decode error from Azure PostgreSQL Flexible Server

[dalextorres]

What does this PR do?

This PR fixes the bug encountered in Azure PostgreSQL Flexible Server in the backend_type column of pg_stat_activity.

There is a bug on Microsoft's side where they send a non valid utf-8 string in that column, leading to decoding errors when trying to fetch this column.

The workaround is to query that same column with ::bytea suffix to convert the field into bytes then parsing backend_type manually. The bug still exists but now we just handle those error cases instead of failing on the whole query.

Motivation

https://datadoghq.atlassian.net/browse/SDBM-1169
https://datadoghq.atlassian.net/browse/SDBM-1197

#incident-31599

A couple of customers where seeing errors utilizing DBM with Azure PG Flexible Server when agent tries to query backend_type from pg_stat_activity. We previously issued a fix but had to revert due to many warnings being logged from the agent.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
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[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.41%. Comparing base (97f5af0) to head (b7fe580).
Report is 2 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
hive	?
hivemq	?
hudi	?
ignite	?
jboss_wildfly	?
kafka	?
postgres	93.27% <77.77%> (+3.93%)	⬆️
presto	?
solr	?

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