Fix live delay computation

[dsilhavy]

The goal of this PR is to fix/adjust live delay calculation:

• Fix live delay calculation for SegmentTimeline manifests for which no valid segment request could be generated with the initial live delay. Increase live delay until a valid segment is found instead of starting playback at the beginning of the DVR window
• When live delay is different from the value initially calculated by computeLiveDelay it gets adjusted in StreamProcessor.findRequestForLiveEdge -> playbackController.setLiveDelay
• If the live delay should be a multiple of the fragment duration use @maxSegmentDuration for multiperiod manifests. For single period manifests iterate through the available AdaptationSets and use the largest segment duration.

This PR is supposed to fix #3227 and #3146

Known Issues:
For SegmentTimeline manifests the fragmentDuration is currently NaN. Related to #3284