Integrate meta-openharmony layer

Closes #657 (closed)

This only adds the meta-openharmony layer (and meta-java as a dependency). It does not enable OpenHarmony features as such, but is a stepping stone for that, and will allow us to add meta-openharmony documentation to the aggregated docs.

flavours/linux/bblayers.conf.sample

@@ -18,6 +18,7 @@ BBLAYERS ?= " \
   ##OEROOT##/../meta-zephyr/meta-zephyr-bsp \
   ##OEROOT##/../meta-zephyr/meta-zephyr-core \
   ##OEROOT##/../oniro/meta-oniro-core \
+  ##OEROOT##/../meta-openharmony \
   ##OEROOT##/../meta-freertos \
   ##OEROOT##/../meta-intel \
   ##OEROOT##/../meta-seco-intel \
@@ -32,4 +33,5 @@ BBLAYERS ?= " \
   ##OEROOT##/../meta-security \
   ##OEROOT##/../meta-riscv \
   ##OEROOT##/../meta-rauc \
+  ##OEROOT##/../meta-java \
   "