[mlir][bufferization] Implement e2e IR transformation for static memory planner
This adds the complete transformation pass that converts multiple
memref.alloc/dealloc pairs into a single arena with subviews.
The offset assignment is intentionally simple (just sequential) - this
establishes the e2e pipeline so we can add smarter bin-packing later.
Tests verify arena sizing, sequential offsets, and that dynamic shapes
or missing deallocations are correctly skipped.