Add coverage for all sniffs identified by testUntested()

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The test suite now compares the full list of sniffs employed by a coding standard against those in the test sample file `//~` annotations and throws an assertion failure if the sample files fail to "cover" all tests.

This acts as a crude kind of "coverage" metric of the sniffs defined in the ruleset, but right now we're only covering about 31 out of 120+ sniffs.

To resolve this, uncomment the `markTestIncomplete()` in `LoadsysStandardTest::testUntested()`. Then repeatedly run `vendor/bin/phpunit` and add new sample files for each remaining sniff name listed. Ideally, there should be two files for each sniff-- one confirming that incorrect style is caught by our ruleset, and another that correct behavior is _not_ caught. The new files should be arranged in the `tests/files/must/` and `tests/files/must_not/` folders. Read the `## Testing` section of the README for more naming details and goals.

Inizia in LoadsysStandardTest::testUntested(), decommenta markTestIncomplete() ed esegui vendor/bin/phpunit per identificare i nomi degli sniff rimanenti. Leggi la sezione Testing del README, quindi aggiungi file di esempio in tests/files/must/ e tests/files/must_not/ per gli sniff rimanenti; il lavoro è completato quando l’intero elenco delle regole è coperto e la suite di test ha esito positivo.

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