.pytool/Plugin/UncrustifyCheck: Add Uncrustify CI plugin

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3748

Adds a new CI plugin for Uncrustify. This is used to check
coding standard compliance of source code to the EDK II C Coding
Standards Specification.

An external dependency is added in the plugin directory to retrieve
the Uncrustify executable. Currently, the executable is from an edk2
fork of the application host in this repository:

https://dev.azure.com/projectmu/Uncrustify/

Note that the Uncrustify application outputs the commit ID that the
application was built from when given the --version parameter.

This ID can be mapped to the version specified in the Uncrustify CI
plugin external dependency file (uncrustify_ext_dep.yaml) such as
73.0.3 by visiting the Uncrustify edk2 fork release pipeline page
which associates the NuGet package version with the commit ID it was
built from:

https://dev.azure.com/projectmu/Uncrustify/_build

The default Uncrustify configuration files are added in the plugin
directory. Additional details are in the Readme.md file added in
the Uncrustify plugin directory.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Tested-by: Michael D Kinney <michael.d.kinney@intel.com>

.pytool/Plugin/UncrustifyCheck/default_file_header.txt

@@ -0,0 +1,9 @@
+/** @file
+  Brief description of the file's purpose.
+
+  Detailed description of the file's contents and other useful
+  information for a person viewing the file for the first time.
+
+  <<Copyright>>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/