chore: copy over password generator for gcp cloud sql database instance

[girdharshubham]

Description of your changes

Copies password generator code from crossplane-contrib/provider-upject-aws (@ytsarev @ravibagri5 @muvaf)

Fixes #549

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

[turkenf]

Thanks for the PR @girdharshubham,

We will review the PR in this week. It would be great if you could add the results to the description after testing the changes you made.