* Convert `scalar_to_vector` to ISLE (AArch64)
Converted the exisiting implementation of `scalar_to_vector` for AArch64 to
ISLE.
Copyright (c) 2022 Arm Limited
* Add support for floats and fix FpuExtend
- Added rules to cover `f32 -> f32x4` and `f64 -> f64x2` for
`scalar_to_vector`
- Added tests for `scalar_to_vector` on floats.
- Corrected an invalid instruction emitted by `FpuExtend` on 64-bit
values.
Copyright (c) 2022 Arm Limited
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