Make MemRefType subclass ShapedType

    MemRefs have the same notion of shape, rank, and fixed element type. This allows us to reuse utilities based on shape for memref.

    All dyn_cast and isa calls for ShapedType have been checked and either modified to explicitly check for vector or tensor, or confirmed to not depend on the result being a vector or tensor.

    Discussion in https://groups.google.com/a/tensorflow.org/forum/#!topic/mlir/cHLoyfGu8y8

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PiperOrigin-RevId: 250945184