refactor!: remove sequential test/suite options in favor of concurrent - #10198

Description

• Closes Deprecate and remove sequential: boolean from test/suite options in favor of its negation concurrent: boolean #10180

Test plan

In test/core, test/config, we already have equivalent tests enumerating both test.sequential and test(.., { concurrent: false }), so just removing sequential ones.

In test/cli, { concurrent: false } tests are missing so replacing existing sequential test with { concurrent: false } with improved coverage.

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