Add performace linting rules

[quasilyte]

This list is work-in-progress. More patterns will be added over time.

Proposed patterns:

• array_values($x)[0] => $x[array_key_first($x)]
• array_keys($x)[0] => array_key_first($x)

When kphp mode is enabled, extra rules can be enabled:

• array_values($x)[0] => array_first_value($x)