Fix visualize tests

[JacobOaks]

PR #404 attempted to improve the tests in visualize_test.go by requiring length equality on the expected/actual ctors.

During CI, this actually uncovered a test failure:

--- FAIL: TestDotGraph (0.02s)
    --- FAIL: TestDotGraph/create_graph_with_one_constructor_and_as_interface_option (0.00s)
        visualize_test.go:453:
                Error Trace:    visualize_test.go:453
                                            visualize_test.go:117
                Error:          "[]" should have 1 item(s), but has 0
                Test:           TestDotGraph/create_graph_with_one_constructor_and_as_interface_option

This is because in this specific test case, the provide was never actually successful because of an error during provide (t5 did not implement io.Reader).

This commit:

• Changes all of the provides that are expected to pass to RequireProvide which will fail if the provide fails.
• Modifies t5 to implement io.Reader.
• Change the test case to expect the provider to only provide the interface in the fx.As (fx.As does not also provide the actual type)
• Add the len check from #404.

This supercedes #404.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (45369ac) 98.40% compared to head (dff4fbd) 98.40%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #405 +/- ## ======================================= Coverage 98.40% 98.40% ======================================= Files 22 22 Lines 1507 1507 ======================================= Hits 1483 1483 Misses 15 15 Partials 9 9 ```

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