feat: generate a subject key identifier when creating a certificate

[kruskall]

What does this PR do?

If a subject key id is omitted, go will generate one using sha1. This is described as method 1 in RFC 5280 Section 4.2.1.2.

Update the code to explicitly pass a subject key id to avoid calling sha1 functions. The new SubjectKeyId is generated using method 1 in RFC 7093 Section 2 which takes 160-bits of the SHA-256 hash.

Why is it important?

When sha1 is not available (e.g. fips only mode) this method will panic.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

[mergify]

This pull request does not have a backport label. Could you fix it @kruskall? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-v8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[michalpristas]

please add UT tests making sure we don't panic on [:20] (we won't not but let's make sure we have changes in golang standard library checked)