Ignore ExpectationFailedError when thrown by the body closure passed to withKnownIssue (#1441)

This fixes an issue where a redundant, second known issue is recorded
when `try #require()` fails within the body closure of `withKnownIssue`.
For example, in the following example code:

```swift
@test func example() {
  withKnownIssue {
    try #require(Bool(false))
  }
}
```

two (known) issues are recorded:

> ✘ Test example() recorded a known issue at
KnownIssueTests.swift:641:9: Expectation failed: Bool(false)
> ✘ Test example() recorded a known issue at
KnownIssueTests.swift:640:18: An API was misused
> ↳ Recorded an error of type ExpectationFailedError representing an
expectation that failed and was already recorded: ...

Of these, only the first should be recorded and the second should be
suppressed.

Fixes rdar://153550847

### Motivation:

It should be possible to use `try #require()` in the body closure passed
to `withKnownIssue`, and _matching_ failures should only cause a single
known issue to be recorded. The second issue shown above describes an
infrastructural `Error`-conforming type which is not generally intended
to be included in the results test authors see, and can cause confusion.

### Modifications:

- When attempting to match an error thrown by a `withKnownIssue` body
closure, ignore the error if it's of type `ExpectationFailedError.
- Add a new unit test validating this, which fails prior to the fix.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: stmontgomery

Sources/Testing/Issues/KnownIssue.swift

@@ -77,6 +77,13 @@ struct KnownIssueScope: Sendable {
 ///   - sourceLocation: The source location to which the issue should be
 ///     attributed.
 private func _matchError(_ error: any Error, in scope: KnownIssueScope, comment: Comment?, sourceLocation: SourceLocation) throws {
+  // ExpectationFailedError is thrown by expectation checking functions to
+  // indicate a condition evaluated to `false`. Those functions record their
+  // own issue, so we don't need to create a new issue and attempt to match it.
+  if error is ExpectationFailedError {
+    return
+  }
+
   let sourceContext = SourceContext(backtrace: Backtrace(forFirstThrowOf: error), sourceLocation: sourceLocation)
   var issue = Issue(kind: .errorCaught(error), comments: [], sourceContext: sourceContext)
   if let context = scope.matcher(issue) {

Tests/TestingTests/KnownIssueTests.swift

@@ -574,6 +574,26 @@ final class KnownIssueTests: XCTestCase {
     await fulfillment(of: [issueRecorded, knownIssueNotRecorded], timeout: 0.0)
   }
 
+  func testKnownIssueWithRequiredExpectationFailure() async {
+    let issueRecorded = expectation(description: "Issue recorded")
+
+    var configuration = Configuration()
+    configuration.eventHandler = { event, _ in
+      guard case .issueRecorded = event.kind else {
+        return
+      }
+      issueRecorded.fulfill()
+    }
+
+    await Test {
+      withKnownIssue {
+        try #require(Bool(false))
+      }
+    }.run(configuration: configuration)
+
+    await fulfillment(of: [issueRecorded], timeout: 0.0)
+  }
+
   func testAsyncKnownIssueThatDoesNotAlwaysOccur() async {
     struct MyError: Error {}