libva: upgrade to 2.19.0

Changelog:
===========
* docs: fix references and descriptions snf focyhrn mstkup
* ci: add build docs test
* win: change default driver search path to bindir
* win: rely on compiler to define link names
* add: Add mono_chrome to VAEncSequenceParameterBufferAV1
* add: Enable support for license acquisition of multiple protected playbacks
* fix: year for version 2.18.0 in NEWS
* fix: use secure_getenv instead of getenv
* trace: Improve and add VA trace log for AV1 encode
* trace: Unify va log message, replace va_TracePrint with va_TraceMsg.

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>