The calculation of the object size may be incorrect when the size of
a field is smaller than the struct alignment. When such a struct is
used in an array field, the decoded object contains wrong values.

The alignment influences the object size. For example the following
struct has a calculated object size of 8 bytes, however due to
alignment the real size of the struct is 12 bytes:

struct test_bool {
  bool b1; /* offset 0, size 1 */
           /* 3-byte padding */
  int i1;  /* offset 4, size 4 */
  bool b2; /* offset 8, size 1 */
           /* 3-byte padding */
};

This commit changes the object size calculation and computes the size
with the offset and size of the last field in the struct (rounded up
by the struct alignment).

Fixes: zephyrproject-rtos#85121
Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>

Support parsing and serializing of struct fields that are defined as a
char array.

Use the token JSON_TOK_STRING_BUF to parse and serialize a string for a
char array, for example:

struct foo {
  const char *str;
  char str_buf[30];
};

struct json_obj_descr foo[] = {
  JSON_OBJ_DESCR_PRIM(struct foo, str, JSON_TOK_STRING),
  JSON_OBJ_DESCR_PRIM(struct foo, str_buf, JSON_TOK_STRING_BUF),
};

The struct 'json_obj_descr' now has an additional union member 'field'
to store the size of the struct field, which is used with the token
'JSON_TOK_STRING_BUF' to determine the element size.

Fixes: zephyrproject-rtos#65200
Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>

Add support for parsing and serializing of following integer types:
'int8_t', 'uint8_t', 'int16_t', 'uint16_t' and 'uint32_t'.

The generic integer token JSON_TOK_INT and JSON_TOK_UINT, in combination
with the field size (set by JSON_OBJ_DESCR_PRIM) allows to parse different
integer types, for example:

struct foo {
  int64_t i64;
  uint32_t u32;
  int16_t i16;
  uint8_t u8;
};

struct json_obj_descr foo[] = {
  JSON_OBJ_DESCR_PRIM(struct foo, i64, JSON_TOK_INT),
  JSON_OBJ_DESCR_PRIM(struct foo, u32, JSON_TOK_UINT),
  JSON_OBJ_DESCR_PRIM(struct foo, i16, JSON_TOK_INT),
  JSON_OBJ_DESCR_PRIM(struct foo, u8, JSON_TOK_UINT),
};

These tokens also support parsing and serializing enums:

enum unsigned_enum { UA=0, UB=1, UC=2 };
enum signed_enum { SA=-1, SB=0, SC=1 };

struct foo {
  enum unsigned_enum u;
  enum signed_enum s;
};

struct json_obj_descr foo[] = {
  JSON_OBJ_DESCR_PRIM(struct foo, u, JSON_TOK_UINT),
  JSON_OBJ_DESCR_PRIM(struct foo, s, JSON_TOK_INT),
};

Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>