Allow back passing a list of Query objects

[florimondmanca]

What does this PR do?

This is a cleanup for #7750

Motivation

#7750 changed QueryManager so that queries=... is expected to be a list of dict, rather than a list of Query.

The motivation was that since queries are statically declared in a queries.py module and referenced from there, we wanted to avoid passing those references directly, and so we unwrapped everything from Query to pass queries=[<dict>, ...].

Yet by doing so we broke backwards compatibility (the PR does have a changelog/Changed label). Here's why:

• On < 7.24.0, checks must be written as QueryManager(queries=[Query(<dict>), ...]).
• On 7.24.0+, checks must be written as QueryManager(queries=[<dict>, ...]) (and it internally converts them to Query).
• And those two are incompatible.

This means users won't be able to upgrade database integrations to versions released after #7750 without also upgrading their Agent to 7.24.0 (which hasn't been released yet, and won't be for a few weeks still, although RCs are available).

For my particular use case (VoltDB), it means I'm not able to write a voltdb that can both work on older Agents (eg 7.22.0, or whichever Agent the customer is using right now) and master. Yet I'd like to avoid requiring the prospect to update their Agents to use an RC — not a very sexy requirement for a sales pitch. :-)

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[codecov]

Codecov Report

Merging #7979 (e82445b) into master (b92cdc3) will increase coverage by 0.26%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
...g_checks_base/datadog_checks/base/utils/db/core.py	100.00% <100.00%> (ø)
datadog_checks_base/tests/test_db.py	100.00% <100.00%> (ø)
gunicorn/datadog_checks/gunicorn/gunicorn.py	82.69% <0.00%> (-1.93%)	⬇️
ibm_mq/tests/test_utils.py
ibm_mq/datadog_checks/ibm_mq/__init__.py
ibm_db2/datadog_checks/ibm_db2/ibm_db2.py
ibm_was/datadog_checks/ibm_was/__about__.py
ibm_mq/datadog_checks/ibm_mq/metrics.py
ceph/tests/test_integration.py
...checks/ibm_mq/collectors/queue_metric_collector.py
... and 193 more

[florimondmanca]

Closing, we don't expect custom checks to be using this anyway, and for my use case (need to support an Agent < 7.24.0 until the final release is out, while making tests pass on master) I'll just try/except my way through things.