tests: remove base64 encoded sections

The base64 sections were added in a time when there was no other way to
do these tests. Now we remove them again to make less "hidden" data in
the test suite.

For several test cases we instead then provide a sequence of binary
octets which is not really better, but I have tried to minimize them.

Closes #16816

tests/data/test397

@@ -11,13 +11,17 @@ compressed
 <reply>
 # Length of not-encoded content is 16512 what is greater than default value of
 # CURL_MAX_WRITE_SIZE (16384)
-<data base64="yes">
-SFRUUC8xLjEgMjAwIE9LDQpEYXRlOiBNb24sIDI5IE5vdiAyMDA0IDIxOjU2OjUzIEdNVA0KU2Vy
-dmVyOiBBcGFjaGUvMS4zLjMxIChEZWJpYW4gR05VL0xpbnV4KSBtb2RfZ3ppcC8xLjMuMjYuMWEg
-UEhQLzQuMy45LTEgbW9kX3NzbC8yLjguMjAgT3BlblNTTC8wLjkuN2QgbW9kX3BlcmwvMS4yOQ0K
-VmFyeTogQWNjZXB0LUVuY29kaW5nDQpDb250ZW50LVR5cGU6IHRleHQvaHRtbDsgY2hhcnNldD1J
-U08tODg1OS0xDQpDb250ZW50LUVuY29kaW5nOiB6c3RkDQpDb250ZW50LUxlbmd0aDogNDcNCg0K
-KLUv/WSAPw0BAIgwMTIzNDU2Nzg5QUJDREVGCgQAfJ9geAAEGh3Sq006l4KvuZw=
+<data>
+HTTP/1.1 200 OK
+Date: Mon, 29 Nov 2004 21:56:53 GMT
+Server: Apache/1.3.31 (Debian GNU/Linux) mod_gzip/1.3.26.1a PHP/4.3.9-1 mod_ssl/2.8.20 OpenSSL/0.9.7d mod_perl/1.29
+Vary: Accept-Encoding
+Content-Type: text/html; charset=ISO-8859-1
+Content-Encoding: zstd
+Content-Length: 47
+
+%hex[%28%b5%2f%fd%64%80%3f%0d%01%00%88%30%31%32%33%34%35%36%37%38%39%41%42%43%44%45%46]hex%
+%hex[%04%00%7c%9f%60%78%00%04%1a%1d%d2%ab%4d%3a%97%82%af%b9%9c]hex%
 </data>
 
 <datacheck>