[Config] No validator for all allowed annotations and their values

[adong]

What happened: We have a list of annotations, however, we dont have validators for them.

Take this sd.yaml as an example.

jobs:
  main:
    requires: [~job1, ~job2]
    image: node:18
    steps:
      - noop: echo "NOOP"
    annotations:
      screwdriver.cd/ram: HIGH
      screwdriver.cd/timeout: 14400a

What you expected to happen:

1. should check if annotation screwdriver.cd/timeout exists or not
2. should check annotation screwdriver.cd/timeout's value 14400a` is valid or not

How to reproduce it: Copy above sd.yaml to https://cd.screwdriver.cd/validator to validate