Mark `NlaStrip.frame_{start,end}` and `NlaStrip.frame_{start,end}_ui` as
to-be-ignored for the library override system, and add a new set of RNA
properties `frame_{start,end}_raw` that the library override system can
use.

Versioning code ensures that overrides on `frame_{start,end}` are
altered to be applied to the `..._raw` counterpart instead.

The override system uses RNA to update properties one-by-one, and the
RNA code trying its best to keep things consistent / valid. This is very
much desired behaviour while a human is editing the data.

However, when the library override system is doing this, it is not
replaying the individual steps (that each end in a valid configuration),
but just setting each property one by one. As a result, the intermediate
state can be invalid (for example moving one strip into another) even
when the end result is perfectly fine.

This is what the `..._raw` properties do -- they set the values without
doing any validation, so they allow the library overrides system to move
strips around.

This assumes that the result of the override is still valid. Logic to
detect invalid situations, and reshuffle the NLA strips if necessary, is
left for a future commit as it is related to #107990 (NLA Vertical
Reorder).

@@ -2243,0 +2248,4 @@
+ * \param to_rna_path The new RNA path. This should be allocated on the heap, and ownership will be
+ * transferred to the library override system.
+ */
+static void version_liboverride_rnapath_change(IDOverrideLibrary *liboverride,

@@ -2243,0 +2265,4 @@
+
+/** Delete the property override, if it exists.
+ *
+ * No-op if the property voerride cannot be found.

@@ -2243,0 +2267,4 @@
+ *
+ * No-op if the property voerride cannot be found.
+ */
+static void version_liboverride_property_delete(IDOverrideLibrary *liboverride,

@@ -2318,0 +2411,4 @@
+
+  int track_index;
+  LISTBASE_FOREACH_INDEX (NlaTrack *, track, &adt->nla_tracks, track_index) {
+    char *rna_path_track = BLI_sprintfN("animation_data.nla_tracks[%d]", track_index);

@@ -760,2 +787,4 @@
   RNA_def_property_update(
       prop, NC_ANIMATION | ND_NLA | NA_EDITED, "rna_NlaStrip_transform_update");
+  /* The `..._ui` properties should NOT be considered for library overrides, as they are meant to
+   * have different behaviour when setting their non-`..._ui` counterparts. */

@@ -3530,0 +3544,4 @@
+                                                       const char *new_rna_path)
+{
+  IDOverrideLibraryProperty *override_property;
+  override_property = BKE_lib_override_library_property_find(override, old_rna_path);

@@ -3530,0 +3551,4 @@
+  }
+
+  /* Remove the property from the lookup mapping. */
+  const bool has_lookup = !ELEM(

@@ -3530,0 +3557,4 @@
+  override_property->rna_path = BLI_strdup(new_rna_path);
+
+  /* Put property back into the lookup mapping, using the new RNA path. */
+  BLI_ghash_insert(override->runtime->rna_path_to_override_properties,