[LBT] set job timeouts
[LBT] set job timeouts

When cluster test gets stuck in an unknown state in LBT, the landing
queue grinds to a halt. Case in point,
https://github.com/libra/libra/actions/runs/58315619

Set timeout on each job in the LBT workflow so that it doesn't wait for
extended time.
  - The build job is limited to 15 minutes, sufficient for 3 retries.
  - Each of the cluster test job (k8s and ecs) is limited to 20 minutes.

Closes: #3019
Approved by: andll

aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core