Define otacerts_zip module in soong

To move the otacerts module from make to soong, define a new module
type otacerts_zip module. This module collects key files from
PRODUCT_DEFAULT_DEV_CERTIFICATE and PRODUCT_EXTRA_OTA_KEYS
(PRODUCT_EXTRA_RECOVERY_KEYS for recovery) to install the zipped file
in etc.
otacerts_zip module is available to recovery to install the
otacerts.zip file in the recovery partition.

Bug: 335364209
Test: Define "PRODUCT_DEFAULT_DEV_CERTIFICATE := \
                 build/make/target/product/security/testkey" and
      m aosp_cf_system_x86_64
Change-Id: Ib5b671e9caef0403c6d9d69bfab29be248d7086c
diff --git a/etc/Android.bp b/etc/Android.bp
index 97788e4..f02c12a 100644
--- a/etc/Android.bp
+++ b/etc/Android.bp
@@ -11,8 +11,9 @@
         "soong-android",
     ],
     srcs: [
-        "prebuilt_etc.go",
         "install_symlink.go",
+        "otacerts_zip.go",
+        "prebuilt_etc.go",
     ],
     testSrcs: [
         "prebuilt_etc_test.go",