[CTFE] Remove "repeat each page" selector. Use value from benchmark args instead.
[CTFE] Remove "repeat each page" selector. Use value from benchmark args instead.

This change:
* Reverts the 25/50/100 repeat values from https://skia-review.googlesource.com/c/8120/
* Removes the "repeat each page" selector and instead uses the value from benchmark args.
* If "--pageset-repeat" is not specified in benchmark args then use "1" as default.
* Adds a note explaining that users can use "--pageset-repeat" to specify a lower/higher repeat value.

BUG=skia:6322

Change-Id: I171d5e8fc897f062f130cdec83f153f80550a57f
Reviewed-on: https://skia-review.googlesource.com/9302
Reviewed-by: Ben Wagner <3ef7217be91069877d94f7907ce5479000772cd3@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot