[clang] [clang][analyzer] Move checker alpha.security.cert.pos.34c into security.PutenvWithAuto (PR #92424)

[Balazs Benics via cfe-commits]

steakhal wrote:

> The "cert" package looks not useful and the checker has not a meaningful name with the old naming scheme.
> Additionally tests and documentation is updated.
> The checker looks good enough to be moved into non-alpha package.

Personally, I prefer reviewing content changes separately from deciding/moving the checker out of alpha. Here are the reasons for doing so:
 - When content is moved around, a different set of mistakes can be made than when updating some doc content.
 - These are orthogonal decisions.

---

I'd suggest to split this PR into two:
 - Keep this PR for updating the content.
 - Have a separate PR for moving it out of alpha.



https://github.com/llvm/llvm-project/pull/92424