New rule: `var` arguments should be initialized before the call

[Chadehoc]

Prerequisites

• [X] This rule has not already been suggested.
• [X] This should be a new rule, not an improvement to an existing rule.
• [X] This rule would be generally useful, not specific to my code or setup.

Suggested rule title

VarArgumentsShouldBeInitialized

Rule description

In #127, there was a discussion on whether var argument should be considered as initializing a variable. Although out arguments should be preferred for that, a confusion in the Delphi compiler (out and var are processed similarly) has lead some teams to accept initialization through var. So, this was suggested as a new rule rather than an improvement or the rule that "variables should be initialized before being used".

This rule states that a variable is "used" when passed as a var argument to a function call, so doing so without the variable being initialized should be warned against.

Rationale

If you do not accept in your code base that initialization could be done via a var argument, then the rationale is the same as stating that a variable should be initialized before being used.

It is especially important for record variables, for which the Delphi compiler does not enforce this basic rule!

[cirras]

Thanks, this seems like a good companion rule to VariableInitialization.

For the rule title, I'm thinking: VarArgumentInitialization