MLBEDSW-10102: Implement Ethos-U55 transposes
This commit implements 2-axis transposes for up to rank 3 shapes using AveragePool for both Ethos-U55 and Ethos-U65.
- Updated shape stride generator to allow asymmetric rank granules.
- Allow null opgroups for substituted stripes in the Ethos-U55 RCS generator.
- Implementation also falls back to a memory copy for non-transposes that may reach the RCS.
Signed-off-by: Philip Hall philip.hall@arm.com Change-Id: I09082e71c931a7a9f433ddb1bdc4ed1128e2e95b