Run pre-merge PR checks on GitHub Actions (#2414)

It adds all pre-merge checks that we currently have in TeamCity to
GitHub Actions.

[CMP-8945](https://youtrack.jetbrains.com/issue/CMP-8945) Run web tests
with the latest and the minimal supported version of browsers
[CMP-8136](https://youtrack.jetbrains.com/issue/CMP-8136) PR checks runs
always by main teamcity config
[CMP-5663](https://youtrack.jetbrains.com/issue/CMP-5663) Run TeamCity
automatically on user PR's after pressing "Approve and Run"

Also, ignored flaky tests (with TODO and follow-up tasks)

## Release Notes
N/A

Author: MatkovIvan

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,25 @@
+name: 'Setup Prerequisites'
+runs:
+  using: "composite"
+  steps:
+    - name: Setup JDK 21
+      uses: actions/setup-java@v4
+      with:
+        java-version: '21'
+        distribution: 'corretto'
+
+    - name: Setup Android SDK
+      uses: android-actions/setup-android@v2
+
+    - name: Setup Gradle
+      uses: gradle/actions/setup-gradle@v4
+      with:
+        # Only save Gradle User Home state for builds on the 'jb-main' branch.
+        # Builds on other branches will only read existing entries from the cache.
+        cache-read-only: ${{ github.ref != 'refs/heads/jb-main' }}
+
+        # Limit the size of the cache entry.
+        # These directories contain instrumented/transformed dependency jars which can be reconstructed relatively quickly.
+        gradle-home-cache-excludes: |
+          caches/jars-9
+          caches/transforms-3

.github/OWNERS

@@ -0,0 +1,23 @@
+name: 'Setup Xcode'
+runs:
+  using: "composite"
+  steps:
+    # List of available Xcode versions:
+    # https://github.com/actions/runner-images/blob/main/images/macos/macos-15-Readme.md#xcode
+    # Note that explicit download is required due to updated support policy:
+    # https://github.com/actions/runner-images/issues/12758#issuecomment-3206748945
+    - name: Setup Xcode version
+      shell: bash
+      run: |
+        sudo xcode-select -s /Applications/Xcode_16.2.app/Contents/Developer
+        xcodebuild -downloadPlatform iOS -buildVersion 18.2
+        /usr/bin/xcodebuild -version
+
+    - name: Cache Xcode DerivedData
+      uses: irgaly/xcode-cache@v1
+      with:
+        key: xcode-cache-deriveddata-${{ github.sha }}
+        restore-keys: xcode-cache-deriveddata-
+        # Only save DerivedData state for builds on the 'jb-main' branch.
+        # Builds on other branches will only read existing entries from the cache.
+        cache-read-only: ${{ github.ref != 'refs/heads/jb-main' }}

.github/actions/build-single-project/action.yml

@@ -0,0 +1,26 @@
+name: Check Public API
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - jb-main
+
+jobs:
+  check-public-api:
+    runs-on: macos-15-xlarge
+    name: Check Public API
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v5
+
+      - name: Setup Prerequisites
+        uses: ./.github/actions/setup-prerequisites
+
+      - name: Setup Xcode
+        uses: ./.github/actions/setup-xcode
+
+      - name: Check Public API
+        run: |
+          ./gradlew jbApiCheck \
+            --no-daemon --stacktrace