Remove baked base addresses; every address should be symbolic

[kcirred]

The backend can bake a kernel's HBM addresses in as arith.constant, computed from a fixed formula —
pointer i at i × 16 GiB. Nothing supports that path: compiler.py:221-229 already marks it
SOON TO BE DEPRECATED, and per docs/designs/level-d-fixture-coverage.md:385 all 28 device
compiles take the symbolic branch. Remove it.

Delete

• _SEGMENT_BYTES, _MAX_POINTER_ARGS, _elem_bytes, _segment_addresses,
  infer_base_addresses_from_ptr_types (backend/compiler.py:113-199); the
  if not options.symbolic_args: block in _make_ktir (:596-600); the .ktir-entry error
  (:651-661).
• SpyreOptions.base_addresses and symbolic_args, the mutual-exclusion check (:291-296), the
  parse_options inference (:434-435).
• lib/Transforms/MaterializeBaseAddresses.cpp, its Passes.td entry
  (include/Transforms/Passes.td:136-185), the Passes.h:27 factory declaration, and the 6 lit
  fixtures under test/Transforms/MaterializeBaseAddresses/.
• bindBaseAddresses / baseAddresses on SpyrecodePipelineOptions (include/Pipeline.h:52-56) and
  the branch at lib/Pipeline.cpp:185-195, whose canonicalize + CSE exist only to fold the
  constants it introduces.
• SpyreLauncher._check_argument_mode_agrees (backend/driver.py:316-351) — with one mode there is
  nothing to disagree with.