Remove uses of attr="${}" from ui.js

[ianb]

We've grown a bunch of uses of:

someHtml = `<button title="${getAttributeText("saveScreenshotSelectedArea")}">`;

We have some quoting in place, but really we just shouldn't do this at all. We have a localizeText() function in ui.js, and should extend that to handle attributes. Maybe <button data-l10n-title="saveScreenshotSelectedArea"> (if it's just titles we're dealing with).

Otherwise if we don't go that route, we should do quoting inline IMHO. We should be able to statically determine that a value is properly quoted for its context, and not rely on secondary functions (like getAttributeText()). Or, maybe, we could name the functions to make it clear, like getHtmlQuotedLocalizedText() – but there's limited savings, because it takes a certain number of letters to say that something is quoted, and function composition or long names doesn't change it much.