This argument will enable mocking of os-layer process invocations,
where the mock behavior will come from replaying a previously-
recorded set of invocations. At the point of process invocation,
the key metadata for the invocation will be looked up in the
recording's manifest, and iff a matching record exists in the
manifest, the process will be mocked out with data derived from
the corresponding recorded process (e.g. stdout, stderr, exit code).

This moves the various copies of port forwarding code in the Device subclasses into the ProtocolDiscovery class.

* move port forwarding to a common location
* throw exception if protocol Uri is not discovered or port forwarding fails
* cancel discovery protocol subscriptions on iOS launches (wasn't happening before)
* fix iOS port forwarding to match other implementations
* add tests

It is not enabled by default in the VM because applications not launched via the tools may try to connect with the debugger. This causes the debugger and the IDE to hang on Mac.

Fixes https://github.com/flutter/flutter/issues/7035

Includes fixes to the VM and analyzer.  Hopefully final RC.

* Use touch to avoid race condition in file modification test

* Remove unused import

* Add --record-to option to flutter tools

This option will cause flutter tools to record all process
invocations that occur and serialize their stdout and stderr
to files that get added to a "recording" ZIP file. This is
part of an effort to be able to test flutter tools in a hermetic
environment.

As a side-benefit, this recording should prove an excellent
attachment to any bug report.

* reapply handle new Observatory URL changes
Fixes https://github.com/flutter/flutter/issues/6843

* allow non numeric IPv4 addresses
Fixes https://github.com/flutter/flutter/issues/7051

We don't need these anymore.

Last full push to dev before `1.21` stable.

Fixes #6915

Changed DefaultTextStyle to consider the TextTheme defined in the context for Bottom Nav Bar (#7042)

* Changed DefaultTextStyle to consider the TextTheme defined in the context

* added regression test for bottom nav bar text themes

* added second regression test for fixed navbar

Fixes https://github.com/flutter/flutter/issues/6947

With this change, they're run via instance methods on an object
obtained through the context. This will allow us to substitute
that object in tests with replay/record versions to allow us to
mock out the os-layer in tests.

* Skip failing input tests

* Only skip on Mac OS