Add additional CHECKs to debug HttpCache::Transaction

https://crbug.com/428819090 indicates that sometimes a cache transaction
is being restarted while `done_headers_create_new_entry_` is true.

Add additional CHECK statements to crash earlier in this case to gather
more information about what is triggering it.

BUG=428819090

Change-Id: Ic0eb13155ded8e43c4c84edc673e1edd60f721fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6719051
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Auto-Submit: Adam Rice <ricea@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Commit-Queue: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1485391}