[ci] run CI on pull requests targeting release/ branches (#5527)

.github/workflows/cuda.yml

@@ -7,6 +7,7 @@ on:
   pull_request:
     branches:
     - master
+    - release/*
 
 env:
   github_actions: 'true'

.github/workflows/optional_checks.yml

@@ -4,6 +4,7 @@ on:
   pull_request:
     branches:
       - master
+      - release/*
 
 jobs:
   all-successful:

.github/workflows/python_package.yml

@@ -7,6 +7,7 @@ on:
   pull_request:
     branches:
     - master
+    - release/*
 
 env:
   CONDA_ENV: test-env

.github/workflows/r_package.yml

@@ -7,6 +7,7 @@ on:
   pull_request:
     branches:
     - master
+    - release/*
 
 env:
   # hack to get around this:

.github/workflows/static_analysis.yml

@@ -9,6 +9,7 @@ on:
   pull_request:
     branches:
     - master
+    - release/*
 
 env:
   COMPILER: 'gcc'

.vsts-ci.yml

@@ -7,6 +7,7 @@ trigger:
     - v*
 pr:
 - master
+- release/*
 variables:
   AZURE: 'true'
   PYTHON_VERSION: '3.10'