twister: Allow sharing hardware platform between variants

[gchwier]

Extended hardware map to share a single board between variants. To run tests for different variants on the same board without re-configuring the hardware map file for each variant, one can extend the platform attribute with board names separated by commas.

Generate hardware map:
${ZEPHYR_BASE}/scripts/twister --generate-hardware-map hardware_map.yml

Update platform with two variants you want to use:

- connected: true
  id: '001050076605'
  platform: nrf5340dk/nrf5340/cpuapp, nrf5340dk/nrf5340/cpuapp/ns
  product: J-Link
  runner: nrfjprog
  serial: /dev/ttyACM1

Run tests:
./scripts/twister -T samples/hello_world --device-testing --hardware-map hardware_map.yml --west-flash=--recover -vv --no-clean -ll debug

DEBUG   - platform filter: ['nrf5340dk/nrf5340/cpuapp', 'nrf5340dk/nrf5340/cpuapp/ns']
...
| Board                       |           ID |   Counter |   Failures |
|-----------------------------|--------------|-----------|------------|
| nrf5340dk/nrf5340/cpuapp    | 001050076605 |         1 |          0 |
| nrf5340dk/nrf5340/cpuapp/ns | 001050076605 |         1 |          0 |

When test is run on a selected board, then all DUTs with same id are locked.