fix(FocusZone|FocusTrapZone): correctly define current document object of the components

[sophieH29]

Fixes #1817

By replacing document to getDocument from focusUtilities we're making sure that the right document object will be used for correct FocusZone and FocusTrapZone function.

getDocument is called with node elements this._root._current and implementation looks like this:

export function getDocument(rootElement?: Element | null): Document | undefined {
  return (rootElement && rootElement.ownerDocument) || document
}

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@3795470). Click here to learn what that means.
The diff coverage is 70.83%.

@@            Coverage Diff            @@
##             master    #1820   +/-   ##
=========================================
  Coverage          ?   69.56%           
=========================================
  Files             ?      875           
  Lines             ?     7596           
  Branches          ?     2219           
=========================================
  Hits              ?     5284           
  Misses            ?     2304           
  Partials          ?        8

Impacted Files	Coverage Δ
...eact/src/lib/accessibility/FocusZone/FocusZone.tsx	89.08% <100%> (ø)
.../src/lib/accessibility/FocusZone/FocusTrapZone.tsx	71.71% <61.11%> (ø)

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[lucivpav]

Looks good to me

[dzearing]

Yep change makes sense. If this is a bug in the other copy, we need to merge the two asap to stop the branching 😀 or fix the bug in both places.

[sophieH29]

Yep change makes sense. If this is a bug in the other copy, we need to merge the two asap to stop the branching 😀 or fix the bug in both places.

@davezuko totally agree on keeping consistency between copies. We encountered the bug when had a case of opening another window with components through window.open, so when document.active was used, it would use the wrong (initial) document object from the parent window. I'll create a PR on Fabric side to replicate the change.

Update: created a PR microsoft/fluentui#10187