Add a script(s) to facilitate release tasks

In https://github.com/envoyproxy/nighthawk/pull/226 we started formalizing the release procedure.
Pending results, it would be good to automate the process where possible.
Candidate tasks for that are:
- assist with bumping the version on master as
- assist with tagging the current revision as
- check the release notes mention the new version
- maybe run the integration tests of the previous release with the new version and call out broken tests, to semi-automate compiling a list of breaking changers.
- add tests that the version emitted in binary `--version` contents and the fortio output transform looks like it ought to in the new release