Add validation for allowed processors in ingest pipelines

[jsoriano]

What does this PR do?

Restrict the processors allowed in ingest pipelines.

Why is it important?

Package compatibility with the stack is going to be controlled by the package spec version. Each version of Kibana will support a range of versions of the spec, so the spec needs to be specific about the features each package can use.

Checklist

• I have added test packages to test/packages that prove my change is effective.
• I have added an entry in spec/changelog.yml.
• I have added a condition so this validation is only enabled on v3.

Related issues

• Part of Package Spec v3 #539
• Part of [Change Proposal] Identify and check additional features that may change between stack versions #559

[jsoriano]

test integrations

[elasticmachine]

Created or updated PR in integrations repostiory to test this vesrion. Check elastic/integrations#7682

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 851d419

cc @jsoriano

[jsoriano]

Reasons for this to be breaking:

• It disallows the use of some processors (that don't seem to be used at the moment).
• It doesn't support the version parameter in pipelines, but it is not used at the moment in Fleet.

[mrodm]

Great! 👍