Remove pre-BlinkGenPropertyTrees codepaths

Now that BlinkGenPropertyTrees (BGPT) has launched, we can remove the
pre-BGPT code.

Bug: 989251
Change-Id: I7c64da9fd5e593436301936abcef3e39198ccbe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1752244
Commit-Queue: Philip Rogers <pdr@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686614}
65 files changed