Cache results from Vibrator HAL getters in wrapper

Cache HAL capabilities and supported effects, since these values do not
change for the same underlying HAL.

Bug: 153418251
Test: atest libvibratorservice_test
Change-Id: I23b9480d23810debb065794071319003360857cb
diff --git a/.gitignore b/.gitignore
index 0d20b64..685e379 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
+*.iml
 *.pyc
+.idea/