Moved common SQL handler methods of common-sql-provider into dedicated module

[dabla]

This PR is linked to the original PR Introduce notion of dialects in DbApiHook, but only contains a small refactoring in which the sql handlers of the common-sql -provider are moved from the sql module to a dedicated handler module, as this will be needed later on to avoid circular import issues. This is to make the review easier as asked by @potiuk. This PR only impacts the common-sql provider, also a dedicated unit test has been added for the handlers.

---

^ Add meaningful description above
Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in newsfragments.

[dabla]

Some things are failing but dunno why

[potiuk]

It seems like installing node to build packages is very unstable recently (connection reset by peer etc.) - we will get it cached soon WIP is here: #43329 cc: @bugraoz93 that should improve stability.

[potiuk]

For now rebasing, commit--amend or close/reopening the PR should retry it.

[dabla]

It seems like installing node to build packages is very unstable recently (connection reset by peer etc.) - we will get it cached soon WIP is here: #43329 cc: @bugraoz93 that should improve stability.

Isn't there a way to be able to re-run a failing step in the ci cd checks of github?

[dabla]

For now rebasing, commit--amend or close/reopening the PR should retry it.

Yeah just did it again, I was a bit worried cause my other PR didn't suffer from those random errors so I though maybe something was wrong in this one.

[bugraoz93]

For now rebasing, commit--amend or close/reopening the PR should retry it.

Yeah just did it again, I was a bit worried cause my other PR didn't suffer from those random errors so I though maybe something was wrong in this one.

This is purely too many trials on node servers trying to download the dependencies and appear in random CI runs