samples, tests: convert string-based twister lists to YAML lists

Twister now supports using YAML lists for all fields that were written
as space-separated lists. Used twister_to_list.py script. Some artifacts
on string length are due to how ruamel dumps content.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

samples/bluetooth/peripheral_ht/sample.yaml

@@ -4,13 +4,21 @@ sample:
 tests:
   sample.bluetooth.peripheral_ht:
     harness: bluetooth
-    platform_allow: qemu_cortex_m3 qemu_x86 nrf51dk_nrf51422 nrf52dk_nrf52832
+    platform_allow:
+      - qemu_cortex_m3
+      - qemu_x86
+      - nrf51dk_nrf51422
+      - nrf52dk_nrf52832
     tags: bluetooth
     integration_platforms:
       - qemu_cortex_m3
   sample.bluetooth.peripheral_ht.frdm_kw41z_shield:
     harness: bluetooth
-    platform_allow: mimxrt1020_evk mimxrt1050_evk mimxrt1060_evk frdm_k64f
+    platform_allow:
+      - mimxrt1020_evk
+      - mimxrt1050_evk
+      - mimxrt1060_evk
+      - frdm_k64f
     tags: bluetooth
     extra_args: SHIELD=frdm_kw41z
     integration_platforms: