Lazy initialize deprecation logger in parser

The deprecation logger in AbstractXContentParser is static. This is done
for performance reasons, to avoid constructing a deprecation logger for
every parser of which there can be many (e.g., one for every document
when scripting). This is fine, but the static here is a problem because
it means we touch loggers before logging is initialized (when
constructing a list setting in Environment which is a precursor to
initializing logging). Therefore, to maintain the previous change (not
constructing a parser for every instance) but avoiding the problems with
static, we have to lazy initialize here. This is not perfect, there is a
volatile read behind the scenes. This could be avoided (e.g., by not
using set once) but I prefer the safety that set once provides. I think
this should be the approach unless it otherwise proves problematic.

Relates #26210