Arm64/SVE: Implemented ConvertToint64 and ConvertToUInt64

[ebepho]

Contributes to #99957

Stress test output:

Passed test: _Sve_r::JIT.HardwareIntrinsics.Arm._Sve.Program.Sve_ConvertToInt64_long_float() : 13
Passed test: _Sve_r::JIT.HardwareIntrinsics.Arm._Sve.Program.Sve_ConvertToInt64_long_double() : 13
Passed test: _Sve_r::JIT.HardwareIntrinsics.Arm._Sve.Program.Sve_ConvertToUInt64_ulong_float() : 13
Passed test: _Sve_r::JIT.HardwareIntrinsics.Arm._Sve.Program.Sve_ConvertToUInt64_ulong_double() : 13
===================Running jitstress===================
------------------- {'JitMinOpts': '1'} -------------------
------------------- {'JitStress': '1'} -------------------
------------------- {'JitStress': '2'} -------------------
------------------- {'JitStress': '1', 'TieredCompilation': '1'} -------------------
------------------- {'JitStress': '2', 'TieredCompilation': '1'} -------------------
------------------- {'TailcallStress': '1'} -------------------
------------------- {'ReadyToRun': '0'} -------------------
===================Running jitstressregs===================
------------------- {'JitStressRegs': '1'} -------------------
------------------- {'JitStressRegs': '2'} -------------------
------------------- {'JitStressRegs': '3'} -------------------
------------------- {'JitStressRegs': '4'} -------------------
------------------- {'JitStressRegs': '8'} -------------------
------------------- {'JitStressRegs': '0x10'} -------------------
------------------- {'JitStressRegs': '0x80'} -------------------
------------------- {'JitStressRegs': '0x1000'} -------------------
------------------- {'JitStressRegs': '0x2000'} -------------------
===================Running jitstress2-jitstressregs===================
------------------- {'JitStress': '2', 'JitStressRegs': '1'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '2'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '3'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '4'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '8'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '0x10'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '0x80'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '0x1000'} -------------------
------------------- {'JitStress': '2', 'JitStressRegs': '0x2000'} -------------------

cc @dotnet/arm64-contrib

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[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

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[amanasifkhalid]

Nit: Can we rename this to SimpleVecOpTest_ValidationLogicForCndSelNarrowing, and do the same for SimpleVecOpTest_ValidationLogicForNarrowing so it's SimpleVecOpTest_ValidationLogicNarrowing? We seem to use the Narrowing suffix on its own elsewhere in the file, so this seems to be a bit more consistent.