Tests: Add ugly integration test for Reports\Full

[MatmaRex]

The class does not really have individually testable components. Provide a big ugly real report data as the input, and a big ugly real generated report as the output. This is not great, but it's something.

The Full report ignores the $phpcsFile argument, so it's easy to mock. Other reports would require a more complicated setup to test.

The test data has been generated from a file simple.php as follows:

<?php

    // This is a space indented line.
    $a = 10;
	// This is a tab indented line.

…using the following command for the output:

phpcs simple.php --basepath=. --report=full --tab-width=4 --no-colors --standard=generic

…and adding this snippet in generateFileReport() for the input:

var_export($report);

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the Contribution Guidelines.
• I grant the project the right to include and distribute the code under the BSD-3-Clause license (and I have the right to grant these rights).
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added XML documentation for the sniff.

[MatmaRex]

I could add some more test cases, but I thought I'd submit this first to see what you think about this kind of test.