test: add VM-based full-stack bluetooth tests

Add tests that check PipeWire <-> PipeWire bluetooth audio streaming for
A2DP, BAP, HFP.  The tests use Qemu VMs and don't require Bluetooth
support from HW / kernel.

Full VM images are not required; similarly to BlueZ kernel tester these
use (read-only) mount of host filesystem.  A monolithic kernel image
with suitable config is required.  The bluetoothd binary installed on
host is used if found; otherwise tests are skipped.

These test depend on https://github.com/pv/pytest-bluezenv which manages
the VM setup.

To launch:

    python3 -m pip install pytest-bluezenv
    meson devenv -C builddir -w . python3 -m pytest test --kernel-build -v

which also builds a kernel image with required options.

test/pytest.ini

@@ -0,0 +1,31 @@
+#
+# To run Pytest tests, use
+#
+# meson devenv -C builddir -w . python3 -m pytest test --kernel-build -v
+#
+# meson devenv -C builddir -w . python3 -m pytest test --kernel /path/to/bzImage -v
+#
+# with bzImage built by yourself, or downloaded from some source eg.
+# https://github.com/pv/bluez-test-functional-kernel/releases/
+#
+# See https://github.com/pv/pytest-bluezenv or run
+#
+# python3 -m pytest test --help
+#
+
+[pytest]
+log_format = %(asctime)s %(levelname)-6s %(name)-20s:  %(message)s
+log_date_format = %Y-%m-%d %H:%M:%S.%f
+log_level = 0
+log_file = test-pytest.log
+markers =
+    vm: tests requiring BlueZ VM environment
+
+addopts =
+    -p pytest_bluezenv
+
+norecursedirs =
+    data
+    .pytest_cache
+
+vm_timeout = 30