Switch from direct intrinsics usage to Vector/Vector64/Vector128/Vector256

We have a bunch of implementations in the core libraries that make direct use of intrinsics. .NET 7 includes cross-platform support via Vector/Vector64/Vector128/Vector256, and we prefer to use those whenever possible over using the intrinsics directly. This issue tracks converting all of our implementations over, or on a case-by-case basis deciding they can't or shouldn't be updated:

• ASCIIUtility.ContainsNonAsciiByte(Vector12<byte>)
• ASCIIUtility.GetIndexOfFirstNonAsciiByte(byte*, nuint)
• ASCIIUtility.GetIndexOfFirstNonAsciiChar(char*, nuint)
• ASCIIUtility.NarrowUtf16ToAscii(char*, byte*, nuint) (#73064)
• ASCIIUtility.WidenAsciiToUtf16(byte*, char*, nuint) (#73055)
• Base64.DecodeFromUtf8(ReadOnlySpan<byte>, Span<byte>, out int, out int, bool)
• Base64.EncodeToUtf8(ReadOnlySpan<byte>, Span<byte>, out int, out int, bool)
• BitArray(bool[]) (https://github.com/dotnet/runtime/pull/63722)
• BitArray.And(BitArray) (https://github.com/dotnet/runtime/pull/63722)
• BitArray.CopyTo(Array, int)
• BitArray.Not(BitArray) (https://github.com/dotnet/runtime/pull/63722)
• BitArray.Or(BitArray) (https://github.com/dotnet/runtime/pull/63722)
• BitArray.Xor(BitArray) (https://github.com/dotnet/runtime/pull/63722)
• BitConverter.DoubleToInt64Bits(double)
• BitConverter.Int32BitsToSingle(int)
• BitConverter.Int64BitsToDouble(long)
• BitConverter.SingleToInt32Bits(float)
• BitOperations.LeadingZeroCount(uint)
• BitOperations.LeadingZeroCount(ulong)
• BitOperations.Log2(uint)
• BitOperations.Log2(ulong)
• BitOperations.PopCount(uint)
• BitOperations.PopCount(ulong)
• BitOperations.RoundUpToPowerOf2(uint)
• BitOperations.RoundUpToPowerOf2(ulong)
• BitOperations.TrailingZeroCount(ulong)
• Decimal.VarDecFromR4(float, out DecCalc)
• Decimal.VarDecFromR8(double, out DecCalc)
• HexConverter.EncodeToUtf16(ReadOnlySpan<byte>, Span<char>, Casing)
• Latin1Utility.GetIndexOfFirstNonLatin1Char(char*, nuint)
• Latin1Utility.NarrowUtf16ToLatin1(char*, byte*, nuint)
• Latin1Utility.WidenLatin1ToUtf16(byte*, char*, nuint)
• Math.BigMul(ulong, ulong, out ulong)
• Math.CopySign(double, double)
• Math.ReciprocalEstimate(double)
• Math.ReciprocalSqrtEstimate(double)
• MathF.CopySign(float, float)
• MathF.ReciprocalEstimate(float)
• MathF.ReciprocalSqrtEstimate(float)
• Matrix4x4.Invert(Matrix4x4, out Matrix4x4)
• Matrix4x4.Lerp(Matrix4x4, Matrix4x4, float)
• Matrix4x4.operator !=(Matrix4x4, Matrix4x4)
• Matrix4x4.operator -(Matrix4x4)
• Matrix4x4.operator -(Matrix4x4, Matrix4x4)
• Matrix4x4.operator *(Matrix4x4, float)
• Matrix4x4.operator *(Matrix4x4, Matrix4x4)
• Matrix4x4.operator +(Matrix4x4, Matrix4x4)
• Matrix4x4.operator ==(Matrix4x4, Matrix4x4)
• Matrix4x4.Permute(Vector128<float>, byte)
• Matrix4x4.Transpose(Matrix4x4)
• OptimizedInboxTextEncoder.GetIndexOfFirstByteToEncode(ReadOnlySpan<byte> data)
• OptimizedInboxTextEncoder.GetIndexOfFirstCharToEncode(ReadOnlySpan<char> data)
• SpanHelpers.IndexOf(ref byte, byte, int) (#73364)
• SpanHelpers.IndexOf(ref char, char, int) (#73368)
• SpanHelpers.IndexOf(ref char, int, ref char, int)
• SpanHelpers.IndexOfAny(ref byte, byte, byte, byte, int) (#73768)
• SpanHelpers.IndexOfAny(ref byte, byte, byte, int) (#73384)
• SpanHelpers.IndexOfAny(ref char, char, char, char, char, char, int) (#73469)
• SpanHelpers.IndexOfAny(ref char, char, char, char, char, int) (#73469)
• SpanHelpers.IndexOfAny(ref char, char, char, char, int) (#73469)
• SpanHelpers.IndexOfAny(ref char, char, char, int) (#73469)
• SpanHelpers.{Last}IndexOf{Any}{Except} (#73768)
• SpanHelpers.SequenceCompareTo(ref byte, int, ref byte, int) (#73475)
• SpanHelpers.SequenceEquals(ref byte, ref byte, nuint) (#67202)
• SpanHelpers.Reverse(ref byte, nuint) (#72780)
• SpanHelpers.Reverse(ref char, nuint) (#72780)
• SpanHelpers.Reverse(ref int, nuint) (#72780)
• String.MakeSeparatorList(ReadOnlySpan<char>, ref ValueListBuilder<int>)
• Utf8Utility.GetPointerToFirstInvalidByte(byte*, int, out int, out int)
• Utf8Utility.TranscodeToUtf8(char*, int, byte*, int, out char*, out byte*)
• VectorMath.ConditionalSelectBitwise(Vector128<double>, Vector128<double>, Vector128<double>)
• VectorMath.ConditionalSelectBitwise(Vector128<float>, Vector128<float>, Vector128<float>)
• VectorMath.Equal(Vector128<float>, Vector128<float>)
• VectorMath.Lerp(Vector128<float>, Vector128<float>, Vector128<float>)
• VectorMath.NotEqual(Vector128<float>, Vector128<float>)