Improve the way Connectors handle certificates

[markfarkas-camunda]

Is your feature request related to a problem? Please describe.

Connectors only supports certificates in JKS format. Also setting the certificate path is different from how other components do it.

Describe the solution you'd like

We should have unified way of setting the certificates, and we should support other certificate formats as well for example PKCS#1 and PKCS#12.

We should have an environment variable CAMUNDA_CA_ZEEBE_CERTIFICATEPATH or ZEEBE_CA_CERTIFICATE_PATH for providing the location of the certificate.

Describe alternatives you've considered

Alternatively we could just improve our docs to make it clearer for customers how they can set up certificates.

Additional context

https://camunda.slack.com/archives/C02JLRNQQ05/p1719241830181899

https://jira.camunda.com/browse/SUPPORT-20948

[hamza-m-masood]

I would like to see support of PKCS#1 and PKCS#8 since that is what zeebe supports.
PKCS#12 is not really important.

[sbuettner]

Decision is to align with the other C8 components and support the same environment variable.