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/android/variable.go b/android/variable.go
index a331439..d144f7d 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -274,8 +274,10 @@
 	AAPTPreferredConfig *string  `json:",omitempty"`
 	AAPTPrebuiltDPI     []string `json:",omitempty"`
 
-	DefaultAppCertificate           *string `json:",omitempty"`
-	MainlineSepolicyDevCertificates *string `json:",omitempty"`
+	DefaultAppCertificate           *string  `json:",omitempty"`
+	ExtraOtaKeys                    []string `json:",omitempty"`
+	ExtraOtaRecoveryKeys            []string `json:",omitempty"`
+	MainlineSepolicyDevCertificates *string  `json:",omitempty"`
 
 	AppsDefaultVersionName *string `json:",omitempty"`