Replace debug key.

This gives better consistency with the release key. Also improve the
debug_sign script to use base64, to eliminate issues with escaping and
newlines.

Bug: 110509075
Test: atest CtsSignedConfigHostTestCases
Change-Id: Id8d7b6b5bee3340803d30d3a4a34c7e62f565a93
diff --git a/tools/signedconfig/debug_public.pem b/tools/signedconfig/debug_public.pem
index f61f813..d9f0d38 100644
--- a/tools/signedconfig/debug_public.pem
+++ b/tools/signedconfig/debug_public.pem
@@ -1,4 +1,4 @@
 -----BEGIN PUBLIC KEY-----
-MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEaAn2XVifsLTHg616nTsOMVmlhBoE
-CGbTEBTKKvdd2hO60pj1pnU8SMkhYfaNxZuKgw9LNvOwlFwStboIYeZ3lQ==
+MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEmJKs4lSn+XRhMQmMid+Zbhbu13Yr
+U1haIhVC5296InRu1x7A8PV1ejQyisBODGgRY6pqkAHRncBCYcgg5wIIJg==
 -----END PUBLIC KEY-----