[mlir][tosa] Migrate tosa to more efficient linalg.conv

Existing linalg.conv2d is not well optimized for performance. Changed to a
version that is more aligned for optimziation. Include the corresponding
transposes to use this optimized version.

This also splits the conv and depthwise conv into separate implementations
to avoid overly complex lowerings.

Reviewed By: antiagainst

Differential Revision: https://reviews.llvm.org/D107504