Reland "Adding absl includes and defines to rtc_* templates."
Reland "Adding absl includes and defines to rtc_* templates."

This reverts commit d161eda477491b2b97fb3f26d229c625a2a0e9b8.

Reason for revert: The problem with iOS trybots should be fixed.

Original change's description:
> Revert "Adding absl includes and defines to rtc_* templates."
>
> This reverts commit 9d8f3850f4c4faad5dc5ab32ab6f2c9c43df7b6c.
>
> Reason for revert: Breaks some trybots: https://build.chromium.org/p/client.webrtc/builders/iOS64%20Release/builds/12793.
>
> Original change's description:
> > Adding absl includes and defines to rtc_* templates.
> >
> > This CL implicitly adds the -I compiler flag and absl macros to WebRTC
> > templates. In order to include absl headers using relative paths, WebRTC
> > needs to ensure that all its build targets are able to see absl headers.
> >
> > This can also be done with public_deps, but WebRTC is trying to avoid
> > it because it creates problems with other build systems. Given this
> > constraint, using rtc_* templates is the most reliable solution.
> >
> > Please note that rtc_* templates are adding absl includes and defines
> > as public_configs, this means that build targets with WebRTC targets
> > in their public_deps will propagate these configs following the GN
> > guideline.
> >
> > Bug: webrtc:8821
> > Change-Id: I4aa594a524f4bd045bcb3e80d76cc27f06fe01d7
> > Reviewed-on: https://webrtc-review.googlesource.com/70367
> > Reviewed-by: Patrik Höglund <b486136ee68458b09c92c86c39f451c87d6ef6a1@webrtc.org>
> > Commit-Queue: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
> > Cr-Commit-Position: refs/heads/master@{#22927}
>
> TBR=b486136ee68458b09c92c86c39f451c87d6ef6a1@webrtc.org,d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org
>
> Change-Id: Id8e1f881c57553386566eb1970f6b9f8632cab37
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: webrtc:8821
> Reviewed-on: https://webrtc-review.googlesource.com/71000
> Reviewed-by: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
> Commit-Queue: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#22928}

TBR=b486136ee68458b09c92c86c39f451c87d6ef6a1@webrtc.org,d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org

Bug: webrtc:8821
Change-Id: I6ee2eda97bbcd4c9be25c9c4073272192b0373f8
Reviewed-on: https://webrtc-review.googlesource.com/71700
Reviewed-by: Patrik Höglund <b486136ee68458b09c92c86c39f451c87d6ef6a1@webrtc.org>
Reviewed-by: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
Commit-Queue: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#23251}
TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc