more worker pools docs improvements
more worker pools docs improvements

* document usage of `?ttl=10s` in `/api/v1/workers`
* better transition to registering with the TSA

[finishes #96698060]

squeedee/concourse,concourse/concourse,longnguyen11288/concourse,sedouard/concourse,longnguyen11288/concourse,CloudCredo/concourse,concourse/concourse,squeedee/concourse,zachgersh/concourse,longnguyen11288/concourse,cjcjameson/concourse,beni55/concourse,concourse/concourse,zachgersh/concourse,CloudCredo/concourse,concourse/concourse,squeedee/concourse,CloudCredo/concourse,zachgersh/concourse,holgero/concourse,holgero/concourse,sedouard/concourse,concourse/concourse,cjcjameson/concourse,Amit-PivotalLabs/concourse,beni55/concourse,beni55/concourse,cjcjameson/concourse,Amit-PivotalLabs/concourse,holgero/concourse,sedouard/concourse,Amit-PivotalLabs/concourse