Slight fixups with FATStorage (#1934)

* Reload the SD card for `CartSD` and all subclasses

* Make `ROMManager::LoadDLDISDCard` delegate to `GetDLDISDCardArgs`

* Add a method overload for `CartSD::SetSDCard`

* Initialize new SD card images with the correct size

* Sync the old card to the host (if applicable) when move-assigning a new one

* Only sync the old card to the host if it's not read-only

* Remove static state in `FATStorage`

- Replace `FF_ReadStorage` and `FF_WriteStorage` with lambda functions
- Keep open and use the single `File` handle throughout the `FATStorage`'s life

src/frontend/qt_sdl/ROMManager.cpp

@@ -759,7 +759,12 @@ std::optional<DSi_NAND::NANDImage> LoadNAND(const std::array<u8, DSiBIOSSize>& a
     return nandImage;
 }
 
-constexpr u64 imgsizes[] = {0, 256, 512, 1024, 2048, 4096};
+constexpr u64 MB(u64 i)
+{
+    return i * 1024 * 1024;
+}
+
+constexpr u64 imgsizes[] = {0, MB(256), MB(512), MB(1024), MB(2048), MB(4096)};
 std::optional<FATStorageArgs> GetDSiSDCardArgs() noexcept
 {
     if (!Config::DSiSDEnable)
@@ -804,12 +809,7 @@ std::optional<FATStorage> LoadDLDISDCard() noexcept
     if (!Config::DLDIEnable)
         return std::nullopt;
 
-    return FATStorage(
-        Config::DLDISDPath,
-        imgsizes[Config::DLDISize],
-        Config::DLDIReadOnly,
-        Config::DLDIFolderSync ? std::make_optional(Config::DLDIFolderPath) : std::nullopt
-    );
+    return FATStorage(*GetDLDISDCardArgs());
 }
 
 void EnableCheats(NDS& nds, bool enable)