File table support for regexp

# Use case

I'm doing multiple `destination_in regexp` checks and would like to have the option of consolidating the expressions within a file table like so `destination_in regexp file /etc/maddy/regexp_rcpt.txt`

# Your idea for a solution

I think similar to `destination` and `destination_in` this would require an additional module `regexp_in` which implements support for tables.

- [x] I'm willing to help with the implementation