[breaking] parser: improve RAII semantics

ROADMAP.md

@@ -4,11 +4,7 @@ Roughly in order of priority:
 
   * Cleanup:
     * Review & cleanup API surface.
-    * Review `parse()` API: add suffixes `_in_situ` and `_in_arena` to clarify
-      intent. Ie:
-      * rename `parse(substr)` to `parse_in_place(substr)`
-      * rename `parse(csubstr)` to `parse_in_arena(csubstr)`
-    * turn calls to `C4_ASSERT()` into calls to `RYML_ASSERT()`
+    * Turn calls to `C4_ASSERT()` into calls to `RYML_ASSERT()`
   * Add emit formatting controls:
     * add single-line flow formatter
     * add multi-line flow formatters
@@ -19,5 +15,4 @@ Roughly in order of priority:
     * add per node format flags
     * (lesser priority) add auto formatter using reasonable heuristics to
       switch between other existing formatters
-  * Optionally preserve Location of nodes in the original YAML source
   * Investigate possibility of comment-preserving roundtrips