[schema] improve normalization of RQLExpressions
Parse and print back the expression instead of manipulating the string.
Among other benefits, it means we don't mangle embedded string constants
that contain commas or multiple spaces.
Closes #6694426
<?xml version="1.0" encoding="UTF-8"?>
<display window-flags="sticky, below" width="185" height="200">
<sensor id="r" module="rqlsensor"/>
<sensor id="FS" module="FontSelector,1,Sans 10 black"/>
<!-- left border -->
<group x="0" width="5" height="200" bg-uri="gfx/border-left.png"/>
<image x="10" y="0" uri="gfx/logo_erudi.png"/>
<array id="results" x="10" y="30"
watch="layout=r:layout, length=r:length">
<label id="lbls1" color="black"
on-enter="r:enter-line"
on-leave="r:leave-line"
on-click="r:click-line"
watch="value=r:result, font=FS:font0, color=r:resultbg"/>
</array>
</display>