.azurepipelines: Enable EDK II CI for stable/* branches

https://bugzilla.tianocore.org/show_bug.cgi?id=3130

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

.azurepipelines/Ubuntu-GCC5.yml

@@ -7,8 +7,10 @@
 ##
 trigger:
 - master
+- stable/*
 pr:
 - master
+- stable/*
 
 jobs:
 - template: templates/pr-gate-build-job.yml

.azurepipelines/Ubuntu-PatchCheck.yml

@@ -5,7 +5,7 @@
 # NOTE: This example monitors pull requests against the edk2-ci branch.  Most
 # environments would replace 'edk2-ci' with 'master'.
 #
-# Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2019 - 2020, Intel Corporation. All rights reserved.<BR>
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
 # https://github.com/tianocore
@@ -16,6 +16,7 @@ trigger: none
 
 pr:
 - master
+- stable/*
 
 pool:
   vmImage: 'ubuntu-latest'

.azurepipelines/Windows-VS2019.yml

@@ -6,9 +6,11 @@
 ##
 trigger:
 - master
+- stable/*
 
 pr:
 - master
+- stable/*
 
 jobs:
 - template: templates/pr-gate-build-job.yml