MB: Flip Linux bots to GN by default.
MB: Flip Linux bots to GN by default.

Change the previous GN configs to build GYP instead
(since we'll keep GYP around for a while) but exclude tests
and examples for that config, since we'll only support the production
code for GYP.

Add new configs for upcoming rename of those bots to GYP instead
of GN.

The Linux32 Debug/Release bots were removed a while back, so
their configs are removed as well.

BUG=webrtc:5949
NOTRY=True

Review-Url: https://codereview.webrtc.org/2277633005
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#13935}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: fe1d191e58514307faa4bb79d87358037661617f

Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk