modules: use dots instead of dashes for session item properties

lib/wp/endpoint.c

modules/module-si-audio-adapter.c

modules/module-si-audio-convert.c

modules/module-si-audio-endpoint.c

modules/module-si-node.c

modules/module-si-standard-link.c

src/scripts/policy-node.lua

tests/modules/si-audio-adapter.c

tests/modules/si-audio-convert.c

tests/modules/si-audio-endpoint.c

tests/modules/si-node.c

tests/modules/si-standard-link.c