Convert uses of the Dangerous APIs to use MemoryMarshal.GetReference (#15532)

Convert uses of the Dangerous APIs to use MemoryMarshal.GetReference (#15532)

* Convert uses of the Dangerous APIs to use MemoryMarshal.GetReference

* Adding Unsafe.AsRef(in...) and using that for ReadOnlySpan GetReference

* Fix typo - add missing bracket.

* Change AsRef(ref...) to AsRef(in...)

* Remove unnecessary whitespace

* Remove Unsafe.AsRef(in...) and its uses.

* Revert "Remove unnecessary whitespace"

This reverts commit 4dbe38cae472e868f74afbabde358f3a7609f6ae.

* Revert "Revert "Remove unnecessary whitespace""

This reverts commit 44d79483423ac9ffcf7c566b79d4a42c6aa15dac.

* Remove extra space to fix formatting.