Improve Formatter API (#1505)

- pass `GrammarVersion` to constructor instead of passing it to each
`format` method
- replace `format(Path): String` with `format(Reader, Appendable)`
- instead of picking which overloads besides `format(String): String`
might be useful, offer a single generalized method that streams input
and output
- add `@Throws(IOException::class)` to ensure that Java callers can
catch this exception
- deprecate old methods

pkl-cli/src/main/kotlin/org/pkl/cli/CliFormatterCommand.kt

@@ -47,7 +47,7 @@ constructor(
   private val errWriter: Writer = System.err.writer(),
 ) : CliCommand(CliBaseOptions()) {
   private fun format(contents: String): String {
-    return Formatter().format(contents, grammarVersion)
+    return Formatter(grammarVersion).format(contents)
   }
 
   private fun writeErrLine(error: String) {