Revert "Introduce PlatformChannelServer"

This reverts commit 687d45999515655e5b0df59638f7bf0199dd1b3c.

Reason for revert:
LUCI Bisection identified this CL as the culprit of a build failure. See the analysis: https://luci-bisection.appspot.com/analysis/b/8785419785842466113

Sample failed build: https://ci.chromium.org/b/8785419785842466113

If this is a false positive, please report it at https://bugs.chromium.org/p/chromium/issues/entry?comment=Analysis%3A+https%3A%2F%2Fluci-bisection.appspot.com%2Fanalysis%2Fb%2F8785419785842466113&components=Tools%3ETest%3EFindit&labels=LUCI-Bisection-Wrong%2CPri-3%2CType-Bug&status=Available&summary=Wrongly+blamed+https%3A%2F%2Fchromium-review.googlesource.com%2Fc%2Fchromium%2Fsrc%2F%2B%2F4370636

Original change's description:
> Introduce PlatformChannelServer
>
> This is a lightweight abstraction around a platform-specific IPC
> endpoint which can accept a single new connection from a
> PlatformChannelServerEndpoint, and return it as a connected
> PlatformChannelEndpoint.
>
> All named pipe connection logic is migrated out of Mojo internals
> and the MOJO_INVITAION_TRANSPORT_TYPE_CHANNEL_SERVER enumeration is
> removed from the Mojo API.
>
> Instead the C++ invitation helpers (and one edge case for Mojo Core
> on Windows) now use PlatformChannelServer to establish a proper
> PlatformChannelEndpoint for use.
>
> All PlatformChannelServerEndpoint support is removed from the
> internal Channel and ConnectionParams objects.
>
> This also effectively fixes long-standing data races in
> ChannelPosix around listening server state which this CL
> removes.
>
> Bug: 1411162
> Fixed: 1426421
> Change-Id: I787c922b7b2eda618f5589c29c7e2af9c8221ab1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4370636
> Reviewed-by: Alex Gough <ajgo@chromium.org>
> Commit-Queue: Ken Rockot <rockot@google.com>
> Cr-Commit-Position: refs/heads/main@{#1122785}
>

Bug: 1411162
Change-Id: I9e454bd355cb5575123564a4744ab4a4c4242517
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4376220
Bot-Commit: luci-bisection@appspot.gserviceaccount.com <luci-bisection@appspot.gserviceaccount.com>
Commit-Queue: luci-bisection@appspot.gserviceaccount.com <luci-bisection@appspot.gserviceaccount.com>
Owners-Override: luci-bisection@appspot.gserviceaccount.com <luci-bisection@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1122796}

• mojo/core/broker_host.cc[diff]
• mojo/core/channel.cc[diff]
• mojo/core/channel.h[diff]
• mojo/core/channel_mac.cc[diff]
• mojo/core/channel_posix.cc[diff]
• mojo/core/channel_posix.h[diff]
• mojo/core/channel_win.cc[diff]
• mojo/core/connection_params.cc[diff]
• mojo/core/connection_params.h[diff]
• mojo/core/core.cc[diff]
• mojo/core/embedder/BUILD.gn[diff]
• mojo/core/invitation_unittest.cc[diff]
• mojo/core/ipcz_driver/invitation.cc[diff]
• mojo/core/ipcz_driver/transport.cc[diff]
• mojo/core/ipcz_driver/transport.h[diff]
• mojo/core/node_controller.cc[diff]
• mojo/core/node_controller.h[diff]
• mojo/public/cpp/platform/BUILD.gn[diff]
• mojo/public/cpp/platform/named_platform_channel.h[diff]
• mojo/public/cpp/platform/platform_channel_server.cc[Deleted - diff]
• mojo/public/cpp/platform/platform_channel_server.h[Deleted - diff]
• mojo/public/cpp/platform/platform_channel_server_endpoint.h[diff]
• mojo/public/cpp/platform/platform_channel_server_mac.cc[Deleted - diff]
• mojo/public/cpp/platform/platform_channel_server_posix.cc[Deleted - diff]
• mojo/public/cpp/platform/platform_channel_server_win.cc[Deleted - diff]
• mojo/public/cpp/platform/tests/BUILD.gn[diff]
• mojo/public/cpp/platform/tests/DEPS[diff]
• mojo/public/cpp/platform/tests/platform_channel_server_unittest.cc[Deleted - diff]
• mojo/public/cpp/system/invitation.cc[diff]