Add redundantEmptyView rule

[mannylopez]

Adds a new redundantEmptyView formatting rule that removes redundant else { EmptyView() } branches in SwiftUI view builders.

In SwiftUI view builders, an if statement without an else branch implicitly produces no content when the condition is false, making an explicit else { EmptyView() } unnecessary.

var body: some View {
    if condition {
        Text("Hello")
-     } else {
-         EmptyView()
    }
}

[codecov]

Codecov Report

❌ Patch coverage is 98.36066% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.30%. Comparing base (c7a265b) to head (b3169c5).
⚠️ Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
Sources/Rules/RedundantEmptyView.swift	98.36%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2470      +/-   ##
===========================================
+ Coverage    95.28%   95.30%   +0.01%     
===========================================
  Files          165      166       +1     
  Lines        25243    25304      +61     
===========================================
+ Hits         24053    24115      +62     
+ Misses        1190     1189       -1     

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[calda]

Yes! Love it! Thank you @mannylopez

[calda]

We're missing a test case for this code path

[mannylopez]

Added testRemoveFullyQualifiedSwiftUIEmptyView

[calda]

I ran this on the Airbnb codebase and found one example where it causes a build failure. However the error seems like a compiler bug to me, not a "real" issue (the example uses a trailing closure, and converting the trailing closure to a non-trailing closure avoids the error, which definitely isn't supposed to happen).

I think it's ok to leave this enabled by default initially, but I will change it to be disabled by default if we get several bug reports like this.