feat(libs): add the unimplemented exports PPSA16064 imports

PPSA16064 (Minecraft Dungeons II, Unreal Engine) failed to load because
these imports had no export:

- libkernel: sceCoredumpWriteUserString
- libSceSaveData: sceSaveDataConvert, sceSaveDataGetConvertProgress
- libSceVideoOut: sceVideoOutVrrPegToFixedRate,
  sceVideoOutVrrUnpegFromFixedRate

None of them is called during the title's start-up, so they are added
as unimplemented exports that throw with their name if a title calls
them. Their signatures are unknown; TechnicalDebt records them. The
built libraries export the NIDs the title imports.

core/libs/prx/libSceSaveData.native/Export.cpp

@@ -724,4 +724,14 @@ int APS5_VABI sceSaveDataDirNameSearchPs4(const SaveDataDirNameSearchCond* cond,
     SAVEDATA_TRACE("dirNameSearchPs4 user=%d -> 0x%08x", cond->user_id, static_cast<unsigned>(rc));
     return rc;
 }
+
+int APS5_VABI sceSaveDataConvert() {
+    NotImplemented_nid_no_patch(__func__);
+    return 0;
+}
+
+int APS5_VABI sceSaveDataGetConvertProgress() {
+    NotImplemented_nid_no_patch(__func__);
+    return 0;
+}
 }

core/libs/prx/libSceVideoOut/Unimplemented.cpp

@@ -17,4 +17,13 @@ int APS5_VABI sceVideoOutColorSettingsSetGamma_(VideoOutColorSettings* settings,
     return sceVideoOutColorSettingsSetGamma(settings, gamma);
 }
 
+int APS5_VABI sceVideoOutVrrPegToFixedRate() {
+    NotImplemented_nid_no_patch(__func__);
+    return 0;
+}
+
+int APS5_VABI sceVideoOutVrrUnpegFromFixedRate() {
+    NotImplemented_nid_no_patch(__func__);
+    return 0;
+}
 }

core/libs/prx/libkernel/System/src/Coredump.cpp

@@ -61,4 +61,9 @@ int APS5_VABI sceCoredumpGetStopInfoCpu(void) {
     NotImplemented_nid_no_patch("kK0DUW1Ukgc");
     return 0;
 }
+
+int APS5_VABI sceCoredumpWriteUserString() {
+    NotImplemented_nid_no_patch(__func__);
+    return 0;
+}
 }

docs/dev/TechnicalDebt.md

@@ -64,6 +64,7 @@ Throughout the project, every function at every stage either **does exactly what
 - [sceFontCreateWritingLine, sceFontWritingLineWritesOrder](../../core/libs/prx/libSceFont/src/WritingLine.cpp) (libSceFont) - signatures and the `SceFontWritingLineStep`/`SceFontCreateWritingLineDetail` layouts (detail id `0x0FD5`) taken from [SharpProspero](https://github.com/SvenGDK/SharpProspero/blob/main/src/SharpProspero/Interop/Font/SceFontStructs.cs), not confirmed on a title; the meaning of the 64-bit writing attribute is unknown
 - [sceFontWritingLineGetOrderingSpace](../../core/libs/prx/libSceFont/src/WritingLine.cpp) (libSceFont) - signature taken from the IDA type database of [Orbital](https://github.com/AlexAltea/orbital/blob/master/tools/ida/db_types.json) and the [SharpProspero](https://github.com/SvenGDK/SharpProspero/blob/main/src/SharpProspero/Interop/Font/SceFont.Engine.cs) bindings, not confirmed on a title. The modelled line applies no spacing, so the head, inline, tail and advance spaces are 0; what spacing the console applies is unknown. A null output throws
 - [sceSaveDataTransferringMountPs4, sceSaveDataDirNameSearchPs4](../../core/libs/prx/libSceSaveData.native/Export.cpp) (libSceSaveData.native) - arguments assumed to be those of `sceSaveDataTransferringMount` and `sceSaveDataDirNameSearch`: KytyPS5 binds both NIDs to the PS5 functions, and [prosper](https://github.com/mattias800/prosper) captured the same result layout on a title for the search. There is no PS4 save area, so the mount returns `NOT_FOUND` and the search reports zero hits
+- [sceCoredumpWriteUserString](../../core/libs/prx/libkernel/System/src/Coredump.cpp), [sceSaveDataConvert, sceSaveDataGetConvertProgress](../../core/libs/prx/libSceSaveData.native/Export.cpp) and [sceVideoOutVrrPegToFixedRate, sceVideoOutVrrUnpegFromFixedRate](../../core/libs/prx/libSceVideoOut/Unimplemented.cpp) - imported by PPSA16064, not called during its start-up and added without an implementation; unknown signatures
 - [sce::Json::Parser::parse](../../core/libs/prx/libSceJson2/Export.cpp) (libSceJson2) - a number that overflows a double (e.g. `1e309`) throws: whether the console rejects the document or stores an infinite real is unknown
 - [sceUserServiceGetNpAccountId](../../core/libs/prx/libSceUserService/Export.cpp) (libSceUserService) - the account id for a user with no linked PSN account is assumed to be 0 with success; libSceNpManager's `sceNpGetAccountIdA` answers the same question with `SCE_NP_ERROR_SIGNED_OUT`
 - [sceUserServiceGetUserColor](../../core/libs/prx/libSceUserService/Export.cpp) (libSceUserService) - the default profile colour is assumed to be blue (0)