Add support for Windows (#492)

This adds support for Windows.
The in-language path separator is still `/`, to ensure Pkl programs are cross-platform.

Log lines are written using CRLF endings on Windows.
Modules that are combined with `--module-output-separator` uses LF endings to ensure
consistent rendering across platforms.

`jpkl` does not work on Windows as a direct executable.
However, it can work with `java -jar jpkl`.

Additional details:

* Adjust git settings for Windows
* Add native executable for pkl cli
* Add jdk17 windows Gradle check in CI
* Adjust CI test reports to be staged within Gradle rather than by shell script.
* Fix: encode more characters that are not safe Windows paths
* Skip running tests involving symbolic links on Windows (these require administrator privileges to run).
* Introduce custom implementation of `IoUtils.relativize`
* Allow Gradle to initialize ExecutableJar `Property` values
* Add Gradle flag to enable remote JVM debugging

Co-authored-by: Philip K.F. Hölzenspies <holzensp@gmail.com>

pkl-core/pkl-core.gradle.kts

@@ -267,6 +267,21 @@ val testAlpineExecutableAmd64 by tasks.registering(Test::class) {
   }
 }
 
+val testWindowsExecutableAmd64 by tasks.registering(Test::class) {
+  dependsOn(":pkl-cli:windowsExecutableAmd64")
+
+  inputs.dir("src/test/files/LanguageSnippetTests/input")
+  inputs.dir("src/test/files/LanguageSnippetTests/input-helper")
+  inputs.dir("src/test/files/LanguageSnippetTests/output")
+
+  testClassesDirs = files(tasks.test.get().testClassesDirs)
+  classpath = tasks.test.get().classpath
+
+  useJUnitPlatform {
+    includeEngines("WindowsLanguageSnippetTestsEngine")
+  }
+}
+
 tasks.testNative {
   when {
     buildInfo.os.isMacOsX -> {
@@ -284,6 +299,9 @@ tasks.testNative {
         dependsOn(testAlpineExecutableAmd64)
       }
     }
+    buildInfo.os.isWindows -> {
+      dependsOn(testWindowsExecutableAmd64)
+    }
   }
 }