Remove "unconditional" messaging from Issue kind .unconditional.

This PR changes the default message for an issue of kind `.unconditional` from
`"Unconditionally failed"` to `"Issue recorded"`.

Although the failure is unconditional at the point it is recorded, the code that
recorded the issue may not be unconditionally executing, so we shouldn't
describe it as unconditional (we just don't know!)

For example, given the following code:

```swift
if case .empty = potatoSack.contents {
  Issue.record("No potatoes left.")
}
```

We would previously log:

> Unconditionally failed: No potatoes left.

Now we'll log:

> Issue recorded: No potatoes left.

Resolves #574.

Author: grynspan

Sources/Testing/Issues/Issue.swift

@@ -171,7 +171,10 @@ extension Issue.Kind: CustomStringConvertible {
   public var description: String {
     switch self {
     case .unconditional:
-      "Unconditionally failed"
+      // Although the failure is unconditional at the point it is recorded, the
+      // code that recorded the issue may not be unconditionally executing, so
+      // we shouldn't describe it as unconditional (we just don't know!)
+      "Issue recorded"
     case let .expectationFailed(expectation):
       if let mismatchedErrorDescription = expectation.mismatchedErrorDescription {
         "Expectation failed: \(mismatchedErrorDescription)"
@@ -457,7 +460,7 @@ extension Issue.Kind.Snapshot: CustomStringConvertible {
   public var description: String {
     switch self {
     case .unconditional:
-      "Unconditionally failed"
+      "Issue recorded"
     case let .expectationFailed(expectation):
       if let mismatchedErrorDescription = expectation.mismatchedErrorDescription {
         "Expectation failed: \(mismatchedErrorDescription)"