The debugger script implementation had its own way to write
uint32_t values to a string as hex values. This removes the
custom code and uses a shared implementation in String16Builder
instead.

The observable effect is that script hashes are now lower-case
and the character sequence is reversed for each 8-character
pair.

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ib21769fbe10c24055fbd3fa9573bc5c2d72f6a74
Reviewed-on: https://chromium-review.googlesource.com/951303Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51801}