Properly check the deapexed files in tests.

The tests in bootclasspath_fragment_test setup the environment to have
two APEXes: a source one and a prebuilt one. Before this change, the
tests for prebuilt incorrectly check the contents in the source one.
This change introduces a new function that properly checks files
deapexed from the prebuilt one.

Bug: 241823638
Test: m nothing
Change-Id: I1865c20b198d50e7ebc8ebfb9f7c71394a225ab7
diff --git a/apex/bootclasspath_fragment_test.go b/apex/bootclasspath_fragment_test.go
index af4fd9f..2ddfd03 100644
--- a/apex/bootclasspath_fragment_test.go
+++ b/apex/bootclasspath_fragment_test.go
@@ -530,9 +530,8 @@
 			java.FixtureSetBootImageInstallDirOnDevice("art", "apex/com.android.art/javalib"),
 		).RunTest(t)
 
-		ensureExactContents(t, result.TestContext, "com.android.art", "android_common_com.android.art_image", []string{
+		ensureExactDeapexedContents(t, result.TestContext, "com.android.art", "android_common", []string{
 			"etc/boot-image.prof",
-			"etc/classpaths/bootclasspath.pb",
 			"javalib/arm/boot.art",
 			"javalib/arm/boot.oat",
 			"javalib/arm/boot.vdex",
@@ -592,9 +591,8 @@
 			java.FixtureSetBootImageInstallDirOnDevice("art", "system/framework"),
 		).RunTest(t)
 
-		ensureExactContents(t, result.TestContext, "com.android.art", "android_common_com.android.art_image", []string{
+		ensureExactDeapexedContents(t, result.TestContext, "com.android.art", "android_common", []string{
 			"etc/boot-image.prof",
-			"etc/classpaths/bootclasspath.pb",
 			"javalib/bar.jar",
 			"javalib/foo.jar",
 		})