Add stacklevel=2 to all warnings and add linter rule preventing regressions in future warning calls.

[MG-MW]

Describe the bug

A lot of the warnings only show the code emitting the warning, which is not really helpful.

It should show the code that is responsible for calling the pandera code, that should be shown in the warning by using the stacklevel argument.

A clear and concise description of what the bug is.

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of pandera.
• (optional) I have confirmed this bug exists on the main branch of pandera.

There are a couple of instances in 4 files, where this is correctly used: see here.

But there are about 18 files, where it is not used correctly: see her.

I have not found a lint rule for pylint, which would enforce correct usage. In ruff there is rule B028, which would enforce this. This would have to wait for a siwtch to ruff as linter (#1293).

Additional context

Some more background on the problems of usage without stacklevel can be found here.