[llvm] [DAG] Add wrappers for insert and extract sub-vector [nfc] (PR #137230)

[Philip Reames via llvm-commits]

preames wrote:

Buildkite is claiming that this change introduces a failure in Flang.Driver/mcmodel.f90 and the flang's parsing of the codemodel command line.  This seems sufficiently unlikely that I'm going to ignore the failure and land the change anyways.  

https://github.com/llvm/llvm-project/pull/137230