fix(filterFilter): correctly handle deep expression objects

Previously, trying to use a deep expression object (i.e. an object whose properties can be objects themselves) did not work correctly. This commit refactors `filterFilter`, making it simpler and adding support for filtering collections of arbitrarily deep objects.

Closes #9698

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BTW, I used "non-IE8" stuff (like `Array.prototype.some/every`) for the sake of conciseness and clarity, so this is not directly back-portable to 1.2.x. If there is interest, I can create a IE8 compatible version (using `for-loops` etc).
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Unrelated newline change (but I promise it is just this one @caitp :smiley:).