Bug 1829189 - Make BeforeSetAttr infallible. r=smaug

rg BeforeSetAttr -l | xargs sed -i 's/nsresult BeforeSetAttr/void BeforeSetAttr/g'
  rg ::BeforeSetAttr -l | xargs sed -i 's/nsresult \(.*\)::BeforeSetAttr/void \1::BeforeSetAttr/g'

Plus trivial fixes, plus clang-format.

The only meaningful changes are in nsXULElement::BeforeSetAttr. Two
things could fail:

chromemargin: I removed it because we don't use the parsed attribute any
other place than here:

  https://searchfox.org/mozilla-central/rev/31f5847a4494b3646edabbdd7ea39cb88509afe2/dom/xul/ChromeObserver.cpp#136

And that deals just fine with it not being parsed.

usercontextid: We have a debug assertion that we don't dynamically change it.
I kept it but I don't think it's worth failing to set the attribute on release for that

Differential Revision: https://phabricator.services.mozilla.com/D176069

dom/html/HTMLImageElement.cpp

@@ -295,9 +295,9 @@ nsMapRuleToAttributesFunc HTMLImageElement::GetAttributeMappingFunction()
   return &MapAttributesIntoRule;
 }
 
-nsresult HTMLImageElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
-                                         const nsAttrValueOrString* aValue,
-                                         bool aNotify) {
+void HTMLImageElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
+                                     const nsAttrValueOrString* aValue,
+                                     bool aNotify) {
   if (aNameSpaceID == kNameSpaceID_None && mForm &&
       (aName == nsGkAtoms::name || aName == nsGkAtoms::id)) {
     // remove the image from the hashtable as needed