[EAK-378] DependsOn: add an action to setup placeholder(empty text)from query

[ala-n]

As an EAK user, I want to be able to set up a placeholder value (also known as an empty text value) for fields using the DependsOn plugin when the value is computed dynamically and depends on configuration.

Example:

    @DialogField(...)
    @TextField()
    @DependsOn(
         action = "set-placeholder",
         query = "@condition ? 'value1' : 'value2'"
    )
    private String field2;