Trace viewer cannot handle traces larger than 256MB (limit on js string size):
https://github.com/catapult-project/catapult/issues/627
And even that is problematic (chrome hangs and crashes).
Split large traces into 100MB parts. Somewhat clumsy, but I don't see any other
solution (other than rewriting trace viewer). At least it works reliably now.

Fixes #15482

Change-Id: I993b5f43d22072c6f5bd041ab5888ce176f272b2
Reviewed-on: https://go-review.googlesource.com/22731Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>