Consider silencing the UnusedVariable violation

[GaryJones]

From #449:

We could also take this opportunity is taken to silence the UnusedVariable violation. It's severity is already dropped down to 1 for WordPress-VIP-Go, which is the same as what the bot runs at (though this may change in the future). From a VIP perspective, unused variables are not important.

What problem would the enhancement address for VIP?

It would reduce the number of violation comments. Although it's not ideal to have values being to variables that are then unused (waste of memory), it's not a severe enough impact to typically worry about.

If clients were keen on this, they could run the VariableAnalyis sniff (or static analysis tools or the inspector plugin for PHPStorm), to find these.

Describe the solution you'd like

Discuss and consider silencing the UnusedVariable violation.

What code should be reported as a violation?

...

What code should not be reported as a violation?

...

[GaryJones]

One example where this is useful, would be when subsequent usages of a variable have a different name:

$foo_example = 'bar';
...
if ( $fo_example ) {...

[GaryJones]

No discussion, so punting.

[rebeccahum]

I'd like to see VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable silenced as well, and the other ones brought down in severity.