Fix for clearing errors after updating and submitting form

[newt10]

Reasons for making this change

There is a bug in the core form (and other variations) where by the form continues to render errors even after the user has fixed them and submitted the form.

The reason this happens is as follows, when the user submits the form, onSubmit handler is called. If validation is enabled then, the handler runs validation functions to check for errors,

      let schemaValidation = this.validate(newFormData);
      let errors = schemaValidation.errors;
      let errorSchema = schemaValidation.errorSchema;
      const schemaValidationErrors = errors;
      const schemaValidationErrorSchema = errorSchema;

If errors are generated then the form State is updated with the new errors

        this.setState(
          {
            errors,
            errorSchema,
            schemaValidationErrors,
            schemaValidationErrorSchema,
          },

If errors are not generated then the state is updated as follows

    this.setState(
      { formData: newFormData, errors: errors, errorSchema: errorSchema },

As we see in the later state update schemaValidationErrors and schemaValidationErrorSchema are not being updated.

This creates a problem because the state for the form is derived using the above values as seen here

    const getCurrentErrors = () => {
      if (props.noValidate) {
        return { errors: [], errorSchema: {} };
      } else if (!props.liveValidate) {
        return {
          errors: state.schemaValidationErrors || [],
          errorSchema: state.schemaValidationErrorSchema || {},
        };
      }
      return {
        errors: state.errors || [],
        errorSchema: state.errorSchema || {},
      };
    };

What this does is that when the last error is fixed on re-submission of the form, the state is calculated from the stale values of schemaValidationErrors & schemaValidationErrorSchema

We fix this by updating the schemaValidationErrors & schemaValidationErrorSchema in the state when form is submitted with errors fixed.

If this is related to existing tickets, include links to them as well. Use the syntax fixes #[issue number] (ex: fixes #123).

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

Tests

Failing test due to this bug

Passing test after fix

[newt10]

This also addresses the PR #2123 with addition of tests.

[epicfaace]

Let's add a UI test like

react-jsonschema-form/packages/core/test/Form_test.js

Lines 630 to 634 in 739a303

	expect(node.querySelector("#root_children_0_name")).to.not.exist;
	Simulate.click(node.querySelector(".array-item-add button"));
	expect(node.querySelector("#root_children_0_name")).to.exist;

that tests the exact scenario for the user that this PR fixes.

[newt10]

Added new UI tests as requested checking for generated HTML

[epicfaace]

Address these changes and then feel free to merge