fix delete_csr test and change flatvector to constant vector

[vlowingkloude]

In this PR, I fixed the format of delete_csr.test. Also, I changed the return vector type of UDF delete_csr from Flat to constant. But the SIGSEGV issue is not solved yet. :(

[Dtenwolde]

I'll take a look why it seg faults! :)

[Dtenwolde]

The seg fault occurs because the query is being run multiple times when the pragma enable_verification is enabled. This pragma will run the query multiple times with different modes. It will rewrite the string using ToString, or serialize and deserialize and re-execute to verify it gets the same results. However, the CSR building is not handling it properly. I am not sure if we should overwrite the CSR or not, but I'll create an issue anyway and deal with this later. The test file now completes as expected :)