[TOSA] Add StatefulOps to TOSA Dialect (#66843)

This patch adds tosa.variable, tosa.variable.read and
tosa.variable.write operators and tests.


Change-Id: I647e2e5c3762d7890b03f6aa7c09a29198b7d355

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Signed-off-by: Jerry Ge <jerry.ge@arm.com>
Co-authored-by: Jerry Ge <jerry.ge@arm.com>