- Compute the escape character values at compile time.
- Use `little_endian::Store32` invariably to write all escaped characters.
- Use 3 slop bytes at the end so that we can safely call `little_endian::Store32` at the end as well.

PiperOrigin-RevId: 677995014
Change-Id: I9d710fff48d0ce0b013e64d726960364c77ea1d7