[llvm] [llvm-lit][test][NFC] Moved cat command tests into separate lit test file (PR #102366)

[Paul Kirth via llvm-commits]

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@@ -0,0 +1,83 @@
+# Check cat command with single file.
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ilovepi wrote:

```suggestion
## Test cat command with a single file.
```

https://github.com/llvm/llvm-project/pull/102366