The `TestTemplateUpdateTriggers` is flaky because of what turned out to be
incompatibility between the Consul agent on the E2E cluster and the HCP Consul
server we were running but hadn't upgraded in a while. Upgrading the HCP Consul
server seems to have fixed the tests, but while I'm in here I've updated this
test suite:
* Port all the consul template test suite off of the old framework, and upgrade to
using e2e "v3" where feasible.
* Clean up some of the assertions in the update triggers test to make the
purpose of the test more clear.
* Remove unnecessary default fields from the job specs.
Closes: #19075
