Add commonly used zone-related data (config snippet and zone file
snippets) as templates which can be reused by filling in different data.
Adjust the isctest.template.Zone to use filepath argument rather than
filename for clarity.
Add isctest.kasp.Key.into_ta() method which convert the key into DS /
DNSKEY trust anchor for BIND config. Add a shared template
trusted.conf.j2 which can be linked to in tests to create the trust
anchor configuration from trust anchor data returned from bootstrap()
function.
This is basically a python replacement for the keyfile_to_static_ds (and
friends) from the conf.sh shell framework.
Some tests don't have a mock root server configured, because they don't
need one. However, these tests might still leak queries to actual name
servers. Add a shared root hints file which can serve as a blackhole for
these queries.
The old name "common" clashes with the convention of system test
directory naming. It appears as a system test directory, but it only
contains helper files.
To reduce confusion and to allow automatic detection of issues with
possibly missing test files, rename the helper directory to "_common".
The leading underscore indicates the directory is different and the its
name can no longer be confused with regular system test directories.
