In some cases, we've seen interactions between Instruments and the iOS
simulator that cause hung instruments and DTServiceHub processes. If
enough instances pile up, the host machine eventually becomes
unresponsive.

Until the underlying issue is resolved, manually kill any orphaned
instances (where the parent process has died and PPID is 1) before
launching another instruments run.

* Disable cocoapods stats

* Add a comment for code readers

* fix new test

* start

* with create

* refactor cocoapod code, add tests

* fix tests

* throw when cocoapod missing

* obj-c projects don’t use use_framework!

* report run target and if it is an emulator

* don't print debug

* rename parameter, remove unused variable

* fix test

* fix comment

* tweak from review, and fix analyzer error

* send custom parameters for the event, not the session

* fix mock

* use the +1 for usage

* add a --machine mode to flutter config

* review feedback

* minor tweaks to the output for flutter_tools

* update test expectations

Snapshot dependency files now backslash-escape dependency paths
containing spaces and backslashes.

See: https://codereview.chromium.org/2966903003/

Previously, the snapshot file was recomputed on every build. We now
record checksums for all snapshot inputs (which are catalogued in the
snapshot dependencies file output alongside the snapshot) and only
rebuild if the checksum for any input file has changed.

This adds a way to run only a subset of the tests.
(The new flags do the same thing as 'pub run test'.)

* Guess sign with the first certificate when multiple are available in machine mode

* review

And fix a typo in a test description.

Previously, xcodeMajorVersion and xcodeMinorVersion returned null unless
xcodeVersionSatisfactory had been called first. We now compute them on
demand, and cache the resultant values.

Also, correct an existing test description.

1. Run all Xcode tool invocations through ProcessManager, which allows
us to mock out failures, etc. for tests.

2. Add said tests.

This reverts commit b2909a24.

This resubmits the following patches:

1. Use Xcode instruments to list devices (#10801)
Eliminates the dependency on idevice_id from libimobiledevice. Instead,
uses Xcode built-in functionality.

2. Make device discovery asynchronous (#10803)
Migrates DeviceDiscovery.devices and all device-specific lookup to be
asynchronous.

Fixes https://github.com/flutter/flutter/issues/10630

* Revert "Make device discovery asynchronous (#10803)"
This reverts commit 972be9c8.

* Revert "Use Xcode instruments to list devices (#10801)"
This reverts commit 37bb5f13.

This is to resolve a failure that looks related to a bad install of Xcode 8.0
on our build bots and should be reinstated when the infra issue is diagnosed
and resolved.

Instruments worked well when this was originally landed, and on the
following commit, but started failing two commits after this originally
landed. Manual invocation of instruments on the build host currently
results in:

```
dyld: Library not loaded: @rpath/InstrumentsAnalysisCore.framework/Versions/A/InstrumentsAnalysisCore
  Referenced from: /Applications/Xcode8.0.app/Contents/Developer/usr/bin/instruments
  Reason: image not found
Abort trap: 6
```

It appears the /Applications/Xcode8.0.app/Contents/Applications
directory (which contains Instruments) is missing on the host.

Migrates DeviceDiscovery.devices and all device-specific lookup to be
asynchronous.

Eliminates the dependency on idevice_id from libimobiledevice. Instead,
uses Xcode built-in functionality.

Moves all remaining calls to tools that are part of the libimobiledevice
suite of tools to the IMobileDevice class. This allows for better
tracking of this dependency, and easier mocking in tests.

All invocations should go via the IMobileDevice class in mac.dart.

Extract out IMobileDevice class, move class to idevice_id, ideviceinfo
(and eventually other libimobiledevice tools such as iproxy) behind this
interface.

Add tests for the case where libimobiledevice is not installed, the case
where it returns no devices, and the case where it returns device IDs.

Eliminates the need for the device/daemon code to get at the iOS/Android
tooling indirectly via Doctor. In tests, we now inject the workflow
objects (or mocks) directly.

* Before tests

* Add the part to trust the cert on the device

* flip the error checks since some are more specific and are more actionable

* add tests

* review

* add min version checks for IntelliJ

* validate the installed versions of IntelliJ and the flutter plugin

* review comments

Relocates two tests alongside other related tests:
* moved code_signing_test.dart alongside other lib/src/ios tests
* moved terminal_test.dart alongside other lib/src/base tests