Exit without an error status when event is not found

This condition isn’t really a ‘success’ per-se…should do a warning
instead.

Also adds an exit even though nothing else can run due to current
logic. But who knows what the future could bring…

If an event is missing, it shouldn’t be marked as a failure because
that is a normal condition of a multi-process runner (race condition).

Instead, handle it as a success to prevent errors and alerts

Fixes #150

This reverts commit 0f57ac9b.

This situation is ‘normal’ in multi-process runners, as one runner may
have picked up the job before another job attempts it.

When that happens, we shouldn’t treat it as an error - rather log it,
and exit normally.

Fixes #150

Bump version to 2.0

Fixes #134

Allow additional internal events via a constant

Ensure the plugin's CLI namespace gets a proper top-level representation

Chunk events queue for cacheability

`Use of undefined constant CRON_CONTROL_ADDITIONAL_INTERNAL_EVENTS - assumed 'CRON_CONTROL_ADDITIONAL_INTERNAL_EVENTS'`

Removal of existing Internal Events is covered by the existing tests.

Necessary since we nest many commands under one namespace

Needs proper warnings about dangers of putting everything here, as they bypass certain locks. Hence the constants.

PHPCS fixes