[llvm] [VectorCombine] support mismatching extract/insert indices for foldInsExtFNeg (PR #126408)

[Simon Pilgrim via llvm-commits]

================
@@ -73,17 +73,11 @@ define <2 x double> @ext1_v2f64(<2 x double> %x, <2 x double> %y) {
 }
 
----------------
RKSimon wrote:

do we have a test case where the dst vector is larger than the src vector?

https://github.com/llvm/llvm-project/pull/126408