feat: Implement the from_utf16_lossy(...) API

[ParkMyCar]

This issue for tracking the implementation of the from_utf16_lossy(...) method that exists on String.

[Kijewski]

String has only one method for this, but shouldn't it be three methods? UTF-16 in native, little and big endian.

[ParkMyCar]

Great point, lets do it! What do you think about supporting the following 6 APIs:

1. from_utf16(...) (native endianness)
2. from_utf16_lossy(...) (native endianness)
3. from_utf16_be(...)
4. from_utf16_be_lossy(...)
5. from_utf16_le(...)
6. from_utf16_le_lossy(...)

[ParkMyCar]

Side note: looks like @CAD97 has a PR to introduce this to the stdlib too! rust-lang/rust#95967

[ParkMyCar]

Also cc @NobodyXu, any thoughts here?

[NobodyXu]

Also cc @NobodyXu, any thoughts here?

I'm not that familiar with utf16 APIs, but this looks alright to me.