MySQL: Fix endianness, introduce mysql_eof() event

We were parsing MySQL using bigendian even though the protocol is
specified as with "least significant byte first" [1]. This is most
problematic when parsing length encoded strings with 2 byte length
fields...

Further, I think, the EOF_Packet parsing was borked, either due to
testing the CLIENT_DEPRECATE_EOF with the wrong endianness, or due to
the workaround in Resultset processing raising mysql_ok(). Introduce a
new mysql_eof() that triggers for EOF_Packet's and remove the fake
mysql_ok() Resultset invocation to fix. Adapt the mysql script and tests
to account for the new event.

This is a quite backwards incompatible change on the event level, but
due to being quite buggy in general, doubt this matters to many.

I think there is more buried, but this fixes the violation of the simple
"SHOW ENGINE INNODB STATUS" and the existing tests continue to
succeed...

[1] https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_basic_dt_integers.html

testing/btest/scripts/base/protocols/mysql/show-engine-innodb-status.test

@@ -0,0 +1,32 @@
+# Test a show engine innodb status invocation.
+
+# @TEST-EXEC: zeek -b -r $TRACES/mysql/mysql-show-engine-innodb-status-no-password.pcap %INPUT > out
+# @TEST-EXEC: btest-diff out
+# @TEST-EXEC: btest-diff mysql.log
+
+@load base/protocols/mysql
+
+event mysql_ok(c: connection, affected_rows: count)
+	{
+	print "mysql ok", affected_rows;
+	}
+
+event mysql_eof(c: connection, is_intermediate: bool)
+	{
+	print "mysql eof", is_intermediate;
+	}
+
+event mysql_result_row(c: connection, row: string_vec)
+	{
+	print "mysql result row", |row|, row[0][:70];
+	}
+
+event mysql_error(c: connection, code: count, msg: string)
+	{
+	print "mysql error", code, msg;
+	}
+
+event mysql_command_request(c: connection, command: count, arg: string)
+	{
+	print "mysql request", command, arg;
+	}

testing/btest/scripts/base/protocols/mysql/wireshark.test

@@ -11,6 +11,11 @@ event mysql_ok(c: connection, affected_rows: count)
 	print "mysql ok", affected_rows;
 	}
 
+event mysql_eof(c: connection, is_intermediate: bool)
+	{
+	print "mysql eof", is_intermediate;
+	}
+
 event mysql_result_row(c: connection, row: string_vec)
 	{
 	print "mysql result row", row;