Add t.Parallel() to SDK tests

Reduces time to run go test ./sdk from 44 seconds to 22.5 seconds.

Requires moving snapshotTestCustomizations from a map to a struct
with individual fields to avoid concurrent map accesses between
subtests.

Test: go test ./sdk
Change-Id: Id6f451ba9cbace8bc7ea915033a795456b85cf3f
diff --git a/sdk/bp_test.go b/sdk/bp_test.go
index c620ac2..d3eaafe 100644
--- a/sdk/bp_test.go
+++ b/sdk/bp_test.go
@@ -73,6 +73,7 @@
 }
 
 func TestAddPropertySimple(t *testing.T) {
+	t.Parallel()
 	set := newPropertySet()
 	for name, val := range map[string]interface{}{
 		"x":   "taxi",
@@ -91,14 +92,17 @@
 }
 
 func TestAddPropertySubset(t *testing.T) {
+	t.Parallel()
 	getFixtureMap := map[string]func() interface{}{
 		"property set":    propertySetFixture,
 		"property struct": propertyStructFixture,
 	}
 
 	t.Run("add new subset", func(t *testing.T) {
+		t.Parallel()
 		for name, getFixture := range getFixtureMap {
 			t.Run(name, func(t *testing.T) {
+				t.Parallel()
 				set := propertySetFixture().(*bpPropertySet)
 				set.AddProperty("new", getFixture())
 				checkPropertySetFixture(t, set, true)
@@ -108,8 +112,10 @@
 	})
 
 	t.Run("merge existing subset", func(t *testing.T) {
+		t.Parallel()
 		for name, getFixture := range getFixtureMap {
 			t.Run(name, func(t *testing.T) {
+				t.Parallel()
 				set := newPropertySet()
 				subset := set.AddPropertySet("sub")
 				subset.AddProperty("flag", false)
@@ -123,12 +129,14 @@
 	})
 
 	t.Run("add conflicting subset", func(t *testing.T) {
+		t.Parallel()
 		set := propertySetFixture().(*bpPropertySet)
 		android.AssertPanicMessageContains(t, "adding x again should panic", `Property "x" already exists in property set`,
 			func() { set.AddProperty("x", propertySetFixture()) })
 	})
 
 	t.Run("add non-pointer struct", func(t *testing.T) {
+		t.Parallel()
 		set := propertySetFixture().(*bpPropertySet)
 		str := propertyStructFixture().(*propertyStruct)
 		android.AssertPanicMessageContains(t, "adding a non-pointer struct should panic", "Value is a struct, not a pointer to one:",
@@ -137,6 +145,7 @@
 }
 
 func TestAddPropertySetNew(t *testing.T) {
+	t.Parallel()
 	set := newPropertySet()
 	subset := set.AddPropertySet("sub")
 	subset.AddProperty("new", "d^^b")
@@ -144,6 +153,7 @@
 }
 
 func TestAddPropertySetExisting(t *testing.T) {
+	t.Parallel()
 	set := propertySetFixture().(*bpPropertySet)
 	subset := set.AddPropertySet("sub")
 	subset.AddProperty("new", "d^^b")
@@ -176,6 +186,7 @@
 }
 
 func TestTransformRemoveProperty(t *testing.T) {
+	t.Parallel()
 	set := newPropertySet()
 	set.AddProperty("name", "name")
 	set.AddProperty("fred", "12")
@@ -188,6 +199,7 @@
 }
 
 func TestTransformRemovePropertySet(t *testing.T) {
+	t.Parallel()
 	set := newPropertySet()
 	set.AddProperty("name", "name")
 	set.AddPropertySet("fred")