[FL-1926] Flipper File Format addons (#753)

* Flipper file format: remove C wrapper
* Flipper file format: open append, float, uint32_t as array, delete key, value count
* Flipper file format: fix scratchpad location
* Flipper file format: add EOL on append
* SubGHZ keystore: update encryption type read and write
* Flipper File Format: enhanced version
* Flipper File Format: fix naming
* Flipper File Format: fix "open" subset naming
* Flipper File Format: tests
* Flipper File Format: file helper naming
* SubGHZ keystore: merge with current state of flipper file format
* Flipper File Format:  update make recipe
* Flipper File Format: open new file method

lib/toolbox/hex.h

@@ -7,14 +7,22 @@ extern "C" {
 #endif
 
 /**
- * @brief Convert ASCII hex value to nibble 
- * 
+ * Convert ASCII hex value to nibble 
  * @param c ASCII character
  * @param nibble nibble pointer, output
  * @return bool conversion status
  */
 bool hex_char_to_hex_nibble(char c, uint8_t* nibble);
 
+/**
+ * Convert ASCII hex values to byte
+ * @param hi hi nibble text 
+ * @param low low nibble text
+ * @param value output value
+ * @return bool conversion status
+ */
+bool hex_chars_to_uint8(char hi, char low, uint8_t* value);
+
 #ifdef __cplusplus
 }
 #endif