feat: add Spectral rules to validate required operation channe and channel servers field

[smoya]

Description

Part of https://github.com/asyncapi/spec/issues/991

Despite the name of the branch, this PR adds two new Spectral rules (packed all together to minimize review efforts and to release asap).

This PR adds the last two new Spectral rules related with https://github.com/asyncapi/spec/issues/991.

1. Checks that the channel field of a required operation (under root) points to a required (under root) channel and not to an optional (under components) channel, no matter if from the same document or from an external.
2. Checks that the servers field of a required channel (under root) points to a subset of required (under root) servers.

Related issue(s) https://github.com/asyncapi/spec/issues/991

[smoya]

I'm sorry but I can't approve until I see "Spectral rules master" added as a skill in your LinkedIn.

Oops, something might went wrong. Can you please check again?

[smoya]

@jonaslagoni @fmvilas FYI I've added to this PR also another rule that checks that the servers field of a required channel (under root) points to a subset of required (under root) servers.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

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[smoya]

/rtm

[asyncapi-bot]

:tada: This PR is included in version 3.0.0-next-major-spec.14 :tada:

The release is available on:

• npm package (@next-major-spec dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: