Reland "pw_bluetooth_proxy: Don't register channels for unknown connections"

This is a reland of commit 1d0c07ffecf0eac74ea5a23abe5a899821f68fd6

There are no changes. The problem was that a downstream project was not
sending connection complete events to ProxyHost.

Original change's description:
> pw_bluetooth_proxy: Don't register channels for unknown connections
>
> Don't create internal L2CAP and AclDataChannel connection state for
> unkown connections when clients attempt to acquire a channel for an
> unkown connection handle. This is necessary for moving the channel
> container from L2capChannelManager to L2capLogicalLink.
>
> Fix memory leak that occurs when clients acquire channels for recently
> disconnected connections or simply invalid connection handles. No
> disconnection event is ever recieved, so the connection state persists
> forever.
>
> Update tests to send connection complete events to ProxyHost.
>
> Fix SendLeConnectionCompleteEvent test utility, which was not setting
> connection_interval or supervision_timeout, causing the event to be
> ignored.
>
> Fixed: 452727552
> Bug: 450060983
> Change-Id: I618cb2208be266fa321c93dc567341ca6a4a361b
> Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/337792
> Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
> Reviewed-by: Jason Graffius <jgraff@google.com>
> Docs-Not-Needed: Jason Graffius <jgraff@google.com>
> Pigweed-Auto-Submit: Ben Lawson <benlawson@google.com>
> Commit-Queue: Ben Lawson <benlawson@google.com>

Bug: 450060983
Change-Id: Ia39bb4eb19dac452be9ff88fd68aa362d159b0c5
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/340092
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Reviewed-by: Jason Graffius <jgraff@google.com>
Docs-Not-Needed: Jason Graffius <jgraff@google.com>
Commit-Queue: Ben Lawson <benlawson@google.com>