Enhance Open Write Fail Action feature to support an option to honor SWR RFC headers.

This is a follow up enhancement for TS-3549 (and related jiras). Open Write Fail Action feature developed with TS-3549 currently supports the following options:

https://docs.trafficserver.apache.org/en/6.0.x/reference/configuration/records.config.en.html#proxy-config-http-cache-open-write-fail-action

0 = default, disable cache and goto origin server
1 = return a 502 error on a cache miss
2 = serve stale if object’s age is under proxy.config.http.cache.max_stale_age, else, goto origin server

This jira is opened to enhance the feature to support a new option to serve stale honoring the SWR RFC headers.