actions/setup-java@v2 - Support different distributions (#132)

* Implement support for custom vendors in setup-java

* minor improvements

* minor refactoring

* Add unit tests and e2e tests

* Update documentation for setup-java@v2 release

* minor improvements

* regenerate dist

* fix comments

* resolve comments

* resolve comments

* fix tests

* Update README.md

Co-authored-by: George Adams <george.adams@microsoft.com>

* Apply suggestions from code review

Co-authored-by: Konrad Pabjan <konradpabjan@github.com>

* fix minor nitpicks

* handle 4th digit

* pull latest main

* Update README.md

* rename adoptium to adopt

* rename adoptium to adopt

* rename adoptium to adopt

* Update README.md

* make java-version and distribution required for action

* update readme

* fix tests

* fix e2e tests

Co-authored-by: George Adams <george.adams@microsoft.com>
Co-authored-by: Konrad Pabjan <konradpabjan@github.com>

docs/switching-to-v2.md

@@ -0,0 +1,35 @@
+# Switching to V2
+## Java distribution
+The major breaking change in V2 is the new mandatory `distribution` input. This field should be specified with one of supported distributions. See [Supported distributions](../README.md#Supported-distributions) for a list of available options.  
+Use the `zulu` keyword if you would like to continue using the same distribution as in V1.
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-java@v2-preview
+  with:
+    distribution: 'zulu'
+    java-version: '11'
+    java-package: jdk # optional (jdk or jre) - defaults to jdk
+- run: java -cp java HelloWorldApp
+```
+
+**General recommendation** — configure CI with the same distribution that is used on your local dev machine.
+
+## Installing custom Java distribution from local file
+Since the `distribution` input is required in V2, you should specify it using `jdkFile` to continue installing Java from a local file on the runner
+```yaml
+steps:
+- run: |
+    download_url="https://github.com/AdoptOpenJDK/openjdk11-binaries/releases/download/jdk-11.0.10%2B9/OpenJDK11U-jdk_x64_linux_hotspot_11.0.10_9.tar.gz"
+    wget -O $RUNNER_TEMP/java_package.tar.gz $download_url
+- uses: actions/setup-java@v2-preview
+  with:
+    distribution: 'jdkFile'
+    jdkFile: ${{ runner.temp }}/java_package.tar.gz
+    java-version: '11.0.0'
+    architecture: x64
+```
+
+## Dropping legacy Java version syntax 1.x
+V1 supported legacy Java syntax such as `1.8` (same as `8`) and `1.8.0.212` (same as `8.0.212`). 
+V2 dropped support for legacy syntax so workflows should be updated accordingly.