Turn iterator $var!=.end() DCHECK() into CHECK() for net

Accessing an invalid iterator can sometimes be a security
issue and these checks are cheap, so upgrade to CHECKs.

Added checks are NotFatalUntil::M130.

`base/not_fatal_until.h` is added using tools/add_header.py,
this may result in some main-file (foo.h for foo.cc) headers
being re-sorted to be first as part `git cl format` of this CL.

For this CL instances were located with a weggli query:

```
weggli --verbose=1 --cpp \
      'DCHECK($var != _.end());' \
   -p 'DCHECK(_.end() != $var);' \
   -p 'DCHECK_NE($var, _.end());' \
   -p 'DCHECK_NE(_.end(), $var);'
```

which should avoid any potentially expensive calculations
of the thing to be matched against .end().

This CL was uploaded by git cl split.

R=rch@chromium.org

Bug: 351745839
Change-Id: I92f5f310f789e84ceb00e5a13c001758b1823b23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5689713
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Alex Gough <ajgo@chromium.org>
Auto-Submit: Alex Gough <ajgo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1326825}