Reduce memory consumption in log parsing scripts

Reduce memory consumption in log parsing scripts

Updated .qpa to .xml conversion scripts to reduce memory consumption.

Before, the script was reading the whole .qpa file and storing it all in
memory. On top of that, it created xml.dom.minidom objects for each
testcase in the .qpa which were also stored in memory.

With this change, we create the .xml file at the same time that we parse
the .qpa which results in only one xml.dom.minidom object being created at
a time.

Components: Scripts

VK-GL-CTS issue: 1813

Change-Id: Iba4cb3bf6a94f57c481eb98a324b28638924075e