AMDGPU: Add detailed buffer, global and flat atomic fadd tests

Precommit for D130579 that will remove manual selection and use
patterns from td files. Tests are grouped based on target features.

All patterns have rtn and no-rtn versions.

buffer atomics patterns are selected based on the intrinsic used
(raw or struct) and the offset operand (imm or vgpr):
_offset raw with imm offset
_offen raw with vgpr offset (or large imm offset)
_idxen struct with imm offset
_bothen struct with vgpr offset (or large imm offset)

global and flat atomics are selected via intrinsic or the atomicrmw fadd.
atomicrmw tests have amdgpu-unsafe-fp-atomics=true and non-system scope
since they get expanded otherwise. atomicrmw fadd does not support vector
type, test float and double.

global atomics patterns are selected based on address type via (global or
flat) intrinsic or atomicrmw fadd with global address(addrspace(1)*).
'no suffix' vgpr addrspace(1)* address
_saddr sgpr addrspace(1)* address

flat atomics patterns are selected via (flat)intrinsic or atomicrmw fadd
with flat address (* - address space 0).

Differential Revision: https://reviews.llvm.org/D131561