This patch migrates iOS device listing from using Xcode instruments to
using the libimobiledevice tools idevice_id and ideviceinfo.

ideviceinfo was previously incompatible with iOS 11 physical devices;
this has now been fixed.

In 37bb5f13 flutter_tools migrated from
libimobiledevice-based device listing on iOS to using Xcode instruments
to work around the lack of support for iOS 11. Using instruments entails
several downsides, including a significantly higher performance hit, and
leaking hung DTServiceHub processes in certain cases when a simulator is
running, necessitating workarounds in which we watched for, and cleaned
up leaked DTServiceHub processes. This patch returns reverts the move to
instruments now that it's no longer necessary.

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.

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.

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.

* 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