Parse encrypted private keys in PKCS#8 format

[jsoriano]

What does this PR do?

Add support to parse encrypted private keys in PKCS#8 format.

Why is it important?

At least OpenSSL 3 uses PKCS#8 format by default. ReadPEMFile silently left private keys on this format encrypted, what produces problems later when trying to use them.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.md

Author's Checklist

• [ ]

Related issues

• Fixes ReadPEMFile doesn't properly read PKCS#8 encrypted keys #134.

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2023-06-23T11:08:01.117+0000

• Duration: 9 min 40 sec

Test stats 🧪

Test	Results
Failed	0
Passed	791
Skipped	11
Total	802

🤖 GitHub comments

Expand to view the GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: c681ccc

History

• 💚 Build #5 succeeded ca9d8f9
• 💚 Build #4 succeeded e28cfbb
• 💚 Build #3 succeeded 900dc38
• 💚 Build #1 succeeded 2265421

cc @jsoriano