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/src/test/files/LanguageSnippetTests/input/api/releaseModule.pkl

@@ -12,7 +12,7 @@ facts {
   }
 
   ["versionInfo"] {
-    current.versionInfo.contains("macOS") || current.versionInfo.contains("Linux")
+    current.versionInfo.contains("macOS") || current.versionInfo.contains("Linux") || current.versionInfo.contains("Windows")
   }
 
   ["commitId"] {

pkl-core/src/test/files/LanguageSnippetTests/input/errors/invalidImportBackslashSep.pkl

@@ -0,0 +1,2 @@
+// In all OSes, the directory separator is forward slash. 
+res = import(#"..\basic\baseModule.pkl"#)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/invalidImportBackslashSep.err

@@ -0,0 +1,12 @@
+–– Pkl Error ––
+Cannot find module `file:///$snippetsDir/input/errors/..%5Cbasic%5CbaseModule.pkl`.
+
+x | res = import(#"..\basic\baseModule.pkl"#)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at invalidImportBackslashSep#res (file:///$snippetsDir/input/errors/invalidImportBackslashSep.pkl)
+
+To resolve modules in nested directories, use `/` as the directory separator.
+
+xxx | text = renderer.renderDocument(value)
+             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)

pkl-core/src/test/files/LanguageSnippetTests/output/projects/badProjectDeps1/bug.err

@@ -1,5 +1,5 @@
 –– Pkl Error ––
-Cannot resolve dependency because file `/$snippetsDir/input/projects/badProjectDeps1/PklProject.deps.json` is malformed.
+Cannot resolve dependency because file `file:///$snippetsDir/input/projects/badProjectDeps1/PklProject.deps.json` is malformed.
 Run `pkl project resolve` to re-create this file.
 
 x | import "@bird/Bird.pkl"

pkl-core/src/test/files/LanguageSnippetTests/output/projects/badProjectDeps2/bug.err

@@ -1,5 +1,5 @@
 –– Pkl Error ––
-Cannot resolve dependency because file `/$snippetsDir/input/projects/badProjectDeps2/PklProject.deps.json` is malformed.
+Cannot resolve dependency because file `file:///$snippetsDir/input/projects/badProjectDeps2/PklProject.deps.json` is malformed.
 Run `pkl project resolve` to re-create this file.
 
 x | import "@bird/Bird.pkl"

pkl-core/src/test/files/LanguageSnippetTests/output/projects/missingProjectDeps/bug.err

@@ -1,5 +1,5 @@
 –– Pkl Error ––
-Cannot resolve dependency because file `PklProject.deps.json` is missing in project directory `/$snippetsDir/input/projects/missingProjectDeps`.
+Cannot resolve dependency because file `PklProject.deps.json` is missing in project directory `file:///$snippetsDir/input/projects/missingProjectDeps/`.
 
 x | import "@birds/Bird.pkl"
            ^^^^^^^^^^^^^^^^^