Add scripts to generate simple test data for certificate verification.

net/data/verify_certificate_chain_unittest/README

Index: net/data/verify_certificate_chain_unittest/README
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+This directory contains test data for verifying certificate chains.
+
+It contains the following types of files:
+
+===============================
+generate-*.py
+===============================
+
+Generates the file for an individual test case. If the python file was
+named generate-XXX.py, then the corresponding output will be named
+XXX.pem.
+
+===============================
+generate-all.sh
+===============================
+
+Runs all of the generate-*.py scripts and does some cleanup.
+
+===============================
+*.pem
+===============================
+
+These files descibe a test case for certificate chain verification.
+
+The input file is a PEM file with blocks for:
+  * The trust store
+  * The certificate chain (target certificate and all intermediaries)
+  * The timestamp to use when verifying
+  * The expected result of verification (success or fail)