[llvm] [VFABI] Improve VFABI unit tests (PR #73907)

[Maciej Gabka via llvm-commits]

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@@ -423,108 +447,167 @@ TEST_F(VFABIParserTest, MissingVectorNameTermination) {
 }
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mgabka wrote:

definitely not for this patch, but at some point would be good to group somehow those tests in this file :)

https://github.com/llvm/llvm-project/pull/73907