refactor(linear_algebra/clifford_algebra): relax typeclasses to semiring

[eric-wieser]

This generalization isn't motivated by any particular result or generalization in the literature; rather, it's motivated by allowing exterior_algebra R M to be redefined as clifford_algebra 0, as this prevents all the results having to be duplicated.

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• [x] depends on: #14303

See also #14819