Before this change ExpPlayerImplInternal dropped a change of the playing period when a change in the timeline occurred that actually changed the playing period but we don't want to update the period queue. This logic also dropped the update of a skipped server side inserted preroll ad for which we want the periodQueue to 'seek' to the stream position after the preroll ad and trigger a SKIP discontinuity.
This change now introduces an exception so that a skipped SSI ad is still causing an update in the period queue which leads to a 'seek' and a discontinuity of type SKIP.
PiperOrigin-RevId: 411607299
Where this introduced an inconsistency (e.g. assigning to something
called `windowIndex`), I generally renamed the transitive closure of
identifiers to maintain consistency (meaning this change is quite
large). The exception is code that interacts with Timeline and Window
directly, where sometimes I kept the 'window' nomenclature.
#minor-release
PiperOrigin-RevId: 407040052
