[tosa] Change VariableOp to align with spec (#142240)
This fixes Tosa VariableOp to align with spec 1.0
- add var_shape attribute to store shape of variable type
- change type attribute to store element type of variable type
- add a builder so previous construction calls still work
- fix up level check of rank to be on variable type instead of initial
value which is optional
- add level check of size for variable type
- add lit tests for variable op's without initial values
- add lit test for variable op with fixed rank but unknown dimension
- add invalid lit test for variable op with unranked type
Signed-off-by: Tai Ly <tai.ly@arm.com>
