fix(compiler): Copy attributes when reinstantiating scf.for ops

The switch to reinstantiating conversion patterns for the conversion
from FHE to TFHE in commit 73fd6c5fe7
caused all attributes of `scf.for` operations to be dropped during the
conversion. This included the custom attribute `parallel`, which is
exploited further down the compilation pipeline to generate parallel
code. As a result, the performance of end-to-end benchmarks dropped
significantly.

This patch copies all attributes of `scf.for` operations upon
reinstantiation, which solves the performance regression.

compiler/lib/Conversion/Utils/Dialects/SCF.cpp

@@ -20,6 +20,8 @@ TypeConvertingReinstantiationPattern<scf::ForOp, false>::matchAndRewrite(
       adaptor.getStep(), adaptor.getInitArgs(),
       [&](OpBuilder &builder, Location loc, Value iv, ValueRange args) {});
 
+  newForOp->setAttrs(adaptor.getAttributes());
+
   // Move operations from old for op to new one
   auto &newOperations = newForOp.getBody()->getOperations();
   mlir::Block *oldBody = oldOp.getBody();