Add exFAT support (#150)

## Summary

* Swap to updated SDCardManager which uses SdFat
* Add exFAT support
  * Swap to using FsFile everywhere
* Use newly exposed `SdMan` macro to get to static instance of
SDCardManager
* Move a bunch of FsHelpers up to SDCardManager

lib/Xtc/Xtc/XtcParser.cpp

@@ -9,6 +9,7 @@
 
 #include <FsHelpers.h>
 #include <HardwareSerial.h>
+#include <SDCardManager.h>
 
 #include <cstring>
 
@@ -33,7 +34,7 @@ XtcError XtcParser::open(const char* filepath) {
   }
 
   // Open file
-  if (!FsHelpers::openFileForRead("XTC", filepath, m_file)) {
+  if (!SdMan.openFileForRead("XTC", filepath, m_file)) {
     m_lastError = XtcError::FILE_NOT_FOUND;
     return m_lastError;
   }
@@ -419,8 +420,8 @@ XtcError XtcParser::loadPageStreaming(uint32_t pageIndex,
 }
 
 bool XtcParser::isValidXtcFile(const char* filepath) {
-  File file = SD.open(filepath, FILE_READ);
-  if (!file) {
+  FsFile file;
+  if (!SdMan.openFileForRead("XTC", filepath, file)) {
     return false;
   }
 

lib/Xtc/Xtc/XtcParser.h

@@ -7,7 +7,7 @@
 
 #pragma once
 
-#include <SD.h>
+#include <SdFat.h>
 
 #include <functional>
 #include <memory>
@@ -80,7 +80,7 @@ class XtcParser {
   XtcError getLastError() const { return m_lastError; }
 
  private:
-  File m_file;
+  FsFile m_file;
   bool m_isOpen;
   XtcHeader m_header;
   std::vector<PageInfo> m_pageTable;