Add recovery support for perf experiments.

This change establishes a place for perf experiments and adds a
script to delay experiments for recovery purposes. For more info
see go/pixel-perf-experiment-whatif.

Bug: 365855872
Test: build/flash, set .Perf__experiments_delay_seconds=10, verify that vendor.perf.allow_experiments=1 after 10 seconds
Flag: NONE controlled by Mendel instead
Change-Id: I78db482542066d5d5646d8c303dbe88054cfe66d
Signed-off-by: Dmitry Skiba <dskiba@google.com>
diff --git a/performance/experiments/sepolicy/property.te b/performance/experiments/sepolicy/property.te
new file mode 100644
index 0000000..e43312c
--- /dev/null
+++ b/performance/experiments/sepolicy/property.te
@@ -0,0 +1,3 @@
+# Properties shared between experiments.
+
+vendor_internal_prop(vendor_perf_allow_experiments_prop)