Convert tests that parse an Extension value to instead

net/data/parse_certificate_unittest/v3_certificate_template.txt

 # This is cert.pem from BoringSSL's tests.
 # https://boringssl.googlesource.com/boringssl/+/5acc423517ec9d53e6cf2cd1b968405e0972c745/ssl/test/runner/cert.pem
 
 # This file is itself valid ascii-der, however uses comments to name various
 # sections (using BEGIN and END). These named sections can be overlapping, and
 # are replaced for generating various test data.
 
 SEQUENCE {
   SEQUENCE {
     [0] {
@@ skipping 92 matching lines @@
           # basicConstraints
           OBJECT_IDENTIFIER { 2.5.29.19 }
           OCTET_STRING {
 #-----BEGIN BASIC_CONSTRAINTS-----
             SEQUENCE {
               BOOLEAN { `ff` }
             }
 #-----END BASIC_CONSTRAINTS-----
           }
         }
+#-----BEGIN EXTENSION-----
+# (For adding in another extension at the end of the list)
+#-----END EXTENSION-----
       }
     }
   }
   SEQUENCE {
     # sha1WithRSAEncryption
     OBJECT_IDENTIFIER { 1.2.840.113549.1.1.5 }
     NULL {}
   }
   BIT_STRING { `003be8786d95d63d6af713192c1bc288ae22abf48d32f57c7167cf2dd11cc2c387e2e9be895ce434ab4891c23f95ae2b479e25786b4f9a10a472fdcff7020cb00a08a45ae2e5747e111d39606ac91f69f32e6326dc9eef6b7a0ae1545798aa729178047e1f8f654d1f0b12ac9c240f84141a552d1fbbf09d09b2085c5932658026` }
 }