Add "Compress" menu item to context menu

The "Compress" functionality already exists, and was so far accessible
only via the 3-dot menu. Adding it to the context menu makes it more
conveniently accessible and discoverable when a mouse is connected to
the device.

Bug: 381002369
Test: atest DocumentsUIGoogleTests:com.android.documentsui.files.MenuManagerTest
Flag: NONE make existing feature more easily accessible and discoverable
Change-Id: I63ffbe4b4da504834e1c499ef93037c1cc46935b