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-commons-test/pkl-commons-test.gradle.kts

@@ -58,6 +58,11 @@ for (packageDir in file("src/main/files/packages").listFiles()!!) {
     }
     doLast {
       val outputFile = destinationDir.get().asFile.resolve("${packageDir.name}.json")
+      if (buildInfo.os.isWindows) {
+        val contents = outputFile.readText()
+        // workaround for https://github.com/gradle/gradle/issues/1151
+        outputFile.writeText(contents.replace("\r\n", "\n"))
+      }
       shasumFile.get().asFile.writeText(outputFile.computeChecksum())
     }
   }