tests: drivers: i2s: Add i2s_additional tests

Extend I2S testing with additional test cases that verify
I2S/TDM driver operation at various configurations.

Check:
- word sizes of 8, 16, 24, 32 and 48 bits;
- one, two, four and eight audio channels configuration;
- data format I2S, Left Justified, Right Justified,
  PCM Long, PCM Short;
- data order MSB and LSB first;
- bit clock and frame clock inversion;
- block size of 6 bytes;
- bit clock continuous and gated;
- internal loopback;
- pingpong option.

Signed-off-by: Sebastian Głąb <sebastian.glab@nordicsemi.no>