`empty_string` triggers in cases where the left hand side isn't a string.

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

Describe the bug

On main (fd7afedfcfe73443a95041fdc51c31d071b97910), the empty_string rule seems to check if the rhs of an equality operator is an empty string literal. This can give false positives when the lhs isn't a string.

It fails in a test using Nimble matchers comparing to an empty string. In this case the suggestion doesn't make sense since .isEmpty isn't available on the type on the lhs.

expect(outputText) == ""

Looking at the implementation, it may also give false positives for types that are StringLiteralConvertible. The suggestions of using isEmpty also wouldn't be possible in that case.

Though, maybe the lint warning message should be changed from assuming the lhs is a string.

Complete output when running SwiftLint, including the stack trace and command used

$ swiftlint lint
path/to/file: [warning:
Empty String Violation: Prefer checking `isEmpty` over comparing `string` to an empty string literal. (empty_string)](warning: Empty String Violation: Prefer checking `isEmpty` over comparing `string` to an empty string literal. (empty_string))
Done linting! Found 1 violations, 0 serious in 1 file.

Environment

• SwiftLint version (run swiftlint version to be sure)? 0.49.1 (main)
• Installation method used (Homebrew, CocoaPods, building from source, etc)? building from source
• Paste your configuration file:

opt_in_rules:
  - empty_string

• Are you using nested configurations? No
  If so, paste their relative paths and respective contents.
• Which Xcode version are you using (check xcodebuild -version)? Xcode 14.0.1
• Do you have a sample that shows the issue?

echo "expect(outputText) == \"\"" | swiftlint lint --no-cache --use-stdin --enable-all-rules

Start with the empty_string rule implementation and reproduce the report using swiftlint lint --no-cache --use-stdin --enable-all-rules with the Nimble-style comparison. Check the rule's handling of equality operands and verify that non-string left-hand sides no longer receive the isEmpty suggestion while string comparisons retain the intended warning.