Migrate swagger Java YAML parser away from 1.1 to YAML 1.2

[ponelat]

Why? Because there are advanced features of YAML that the OpenAPI specification doesn't support, and these are still acted upon within the current YAML parser.

A simple example is using no as a boolean false, the classic Norway country code can be confused for false :D

country_codes:
# - ...
  - no # Get's parsed as false by YAML 1.1

ping @frantuma in case I'm recreating an already existing issue.