Add API describe.sequential to be able to override --sequence.concurrent

[o-alexandrov]

Clear and concise description of the problem

Related to #3573 (thank you for the feature).
There's one case users would probably miss:

• when setting --sequence.concurrent, there's no way to override this behavior for an individual describe suite
  • for example, we have describe.concurrent now to set the sequence.concurrent behavior for an individual describe, but if a user would set .concurrent by default, there's no way to add a sequential override for an individual describe

Suggested solution

Please consider to add API: describe.sequential(...), so a user could override --sequence.concurrent for a specific describe.

Alternative

No response

Additional context

No response

Validations

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