New Rule: Named Struct Arguments

[justinkaseman]

Description

Add a solhint rule to enforce the following recommendation from the Chainlink contracts style guide:

Structs should be constructed with named arguments. This prevents accidental assignment to the wrong field and makes the code more readable.

// Good
function setConfig(uint64 _foo, uint64 _bar, uint64 _baz) external {
 config = Config({
   foo: _foo,
   bar: _bar,
   baz: _baz
 });
}

// Bad
function setConfig(uint64 _foo, uint64 _bar, uint64 _baz) external {
 config = Config(_foo, _bar, _baz);
}

https://github.com/smartcontractkit/chainlink/blob/3a74dc13b2d42316803b26b2254caa12f7beccb4/contracts/STYLE_GUIDE.md?plain=1#L389

Steps

1. Make a solhint rule and open a PR against this repository's master branch
2. Once merged, open a PR to the Chainlink repository that updates the STYLE_GUIDE.md to reference the new rule