Keep frames when providing insets to freeform windows

A previous CL [1] removed all frames and insets except for caption and
ime provided to freeform windows. However, some frames should be kept.

For example, according to WindowInsets#getPrivacyIndicatorBounds, this
value should not be null when there's a privacy indicator.

This change adds back frames for freeform windows.

[1] Ife41a37082a65db50c7bb5b75690db5bc3cb0bd2

Bug: 226707036
Test: android.server.wm.PrivacyIndicatorBoundsTests
Change-Id: I9a7aafdfbbb9490ba646dc113b135515781cdb82