Confusing discriminator behaviour

[hotrush]

Context

Would be good to get much more clear discriminator behaviour

Current Behavior

This issue #2190 says that schema name (or title, doesn't matter) used as options values in the dropdown, but it's confusing because:

• user doesn't know what value for what field you need to send (discriminator field is not even highlighted or so)
• what schema from oneOf list relates to what discriminator value
• schema name/title is not always self-explanatory, it's not named like SchemaWhenField1HasValueOfFoo

Expected Behavior

• dropdown should be located at the discriminator field level
• dropdown values should contain keys from discriminator mapping (actual field values) (if provided of course)