Android: Fix JNI edge cases, read Java strings as real UTF-8

- Scoped storage no longer flips on while no activity is registered: whether
  legacy storage was preserved is fixed per install, so it's asked once.
- Free space reads as unknown (-1), not 0 bytes, without an activity.
- Strings from Java (file listings and info, crash history, the camera list,
  the input debug string) go through GetJavaString, so names with characters
  outside the BMP aren't mangled, and a null string can't crash the crash
  history.
- Requests (inputbox, browse_*) whose command can't be delivered are failed
  instead of left waiting forever.
- A font that fails to load uses the default typeface (-1) instead of font 0,
  and is retried later if there was no activity yet. Missing exception checks
  added in the text renderer.
- Method IDs and the storage callbacks are looked up once in JNI_OnLoad.
- Unknown permissions are logged correctly.

Also removes what was left of Moga support, the unused backbuffer format and
a stray MessageBox macro, and tidies System_GetCameraDeviceList.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

UI/SystemInfoScreen.cpp

@@ -302,14 +302,6 @@ void SystemInfoScreen::CreateDeviceInfoTab(UI::LinearLayout *deviceSpecs) {
 	}
 	versionInfo->Add(new InfoItem(si->T("Shading Language"), draw->GetInfoString(InfoField::SHADELANGVERSION)));
 
-#if PPSSPP_PLATFORM(ANDROID)
-	std::string moga = System_GetProperty(SYSPROP_MOGA_VERSION);
-	if (moga.empty()) {
-		moga = si->T("(none detected)");
-	}
-	versionInfo->Add(new InfoItem("Moga", moga));
-#endif
-
 	if (gstate_c.GetUseFlags()) {
 		// We're in-game, and can determine these.
 		// TODO: Call a static version of GPUCommon::CheckGPUFeatures() and derive them here directly.