Introduce with_partial_data chaining for be_result matchers

[marian13]

with_data forces the user to pass full data all the time.

What if we need to check a particular key only and other keys are NOT the subject of a spec?

# matchers with full data
expect(result).to be_success.with_data({foo: :bar, baz: :qux})

# matchers with partial data
expect(result).to be_success.with_partial_data({{foo: :bar})