[mlir][llvm] Add arm_streaming LLVM function attributes

[mlir][llvm] Add arm_streaming LLVM function attributes

This patch adds two optional attributes to 'llvm.func' op for the Armv9
Streaming SVE (SSVE) mode [1] that map 1-1 with LLVM function attributes [2]:

  * arm_streaming -> aarch64_pstate_sm_enabled
  * arm_locally_streaming -> aarch64_pstate_sm_body

Streaming-mode is part of the interface (ABI) for functions with the
first attribute and it's the responsibility of the caller to manage
PSTATE.SM on entry/exit to functions with this attribute [3]. The LLVM
backend will emit 'smstart sm' / 'smstop sm' [4] around calls to
streaming functions.

In locally streaming functions PSTATE.SM is kept internal and managed by
the callee on entry/exit. The LLVM backend will emit 'smstart sm' /
'smstop sm' in the prologue / epilogue for functions with this
attribute.

The integration test for SSVE has been updated to no longer use the
passthrough mechanism that's intended for prototyping.

PATCH [1 / 2] in series for RFC: https://discourse.llvm.org/t/rfc-supporting-armv9-scalable-matrix-extension-sme-streaming-sve-ssve-mode-in-mlir/70678

[1] https://developer.arm.com/documentation/ddi0616/aa
[2] https://llvm.org/docs/AArch64SME.html#introduction
[3] https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#671pstatesm-interfaces
[4] https://developer.arm.com/documentation/ddi0602/2023-03/Base-Instructions/SMSTART--Enables-access-to-Streaming-SVE-mode-and-SME-architectural-state--an-alias-of-MSR--immediate--

Reviewed By: awarzynski, dcaballe, WanderAway

Differential Revision: https://reviews.llvm.org/D150932