Use distroless/static image instead of distroless/base since glibc is not used

[vilmosmartinek]

Description of your changes

This pull request changes the base image of the function to gcr.io/distroless/static-debian12:nonroot.

Fixes #48

I have:

• Read and followed Crossplane's contribution process.
  - [ ] Added or updated unit tests for my change.

[jbw976]

ah nice @vilmosmartinek, this looks like a good improvement to make. Thank you for taking the initiative to do so 🙇‍♂️ - it's actually particularly on my mind as I just finished writing up the security self-assessment in crossplane/crossplane#6143 😉

I see that you've opened similar PRs across a few other function repos and also the template repo (crossplane/function-template-go#88), thank you for being thorough.

Let's see if we can get these all merged and new versions of the functions published.

Were you able to do some local testing already to build with this change and verify the function works well still? I don't think there's much in the way of e2e tests here that would test that automatically...