Abstract prebuilt_etc into prebuilt_file

Bug: 215723302
Test: bp2build.sh
Test: mixed_{libc,droid}.sh
Change-Id: I0dab7a6209320e31cfdfe1ce28cacd4f37c11024
diff --git a/bp2build/prebuilt_etc_conversion_test.go b/bp2build/prebuilt_etc_conversion_test.go
index 3a5d5bb..a001972 100644
--- a/bp2build/prebuilt_etc_conversion_test.go
+++ b/bp2build/prebuilt_etc_conversion_test.go
@@ -45,7 +45,7 @@
 }
 `,
 		expectedBazelTargets: []string{
-			makeBazelTarget("prebuilt_etc", "apex_tz_version", attrNameToString{
+			makeBazelTarget("prebuilt_file", "apex_tz_version", attrNameToString{
 				"filename":    `"tz_version"`,
 				"installable": `False`,
 				"src":         `"version/tz_version"`,
@@ -75,7 +75,7 @@
 }
 `,
 		expectedBazelTargets: []string{
-			makeBazelTarget("prebuilt_etc", "apex_tz_version", attrNameToString{
+			makeBazelTarget("prebuilt_file", "apex_tz_version", attrNameToString{
 				"filename":    `"tz_version"`,
 				"installable": `False`,
 				"src": `select({
@@ -114,7 +114,7 @@
 }
 `,
 		expectedBazelTargets: []string{
-			makeBazelTarget("prebuilt_etc", "apex_tz_version", attrNameToString{
+			makeBazelTarget("prebuilt_file", "apex_tz_version", attrNameToString{
 				"filename":    `"tz_version"`,
 				"installable": `False`,
 				"src": `select({