Adding option to disable jetstream ascii art

[renevo]

This option is not available in the config, and is only accessable to embeded servers where when using custom loggers can look pretty terrible

• Branch rebased on top of current main (git pull --rebase origin main)
• Changes squashed to a single commit (described here)
• Build is green in Travis CI
• You have certified that the contribution is your original work and that you license the work to the project under the Apache 2 license

Changes proposed in this pull request:

• Add ability to disable the jetstream ascii art banner on embeded servers as when using custom logging skews the ascii art.

INFO[2023-06-20T21:00:54-07:00] Starting JetStream                           
INFO[2023-06-20T21:00:54-07:00] _ ___ _____ ___ _____ ___ ___   _   __  __   
INFO[2023-06-20T21:00:54-07:00] _ | | __|_   _/ __|_   _| _ \ __| /_\ |  \/  | 
INFO[2023-06-20T21:00:54-07:00] | || | _|  | | \__ \ | | |   / _| / _ \| |\/| | 
INFO[2023-06-20T21:00:54-07:00] \__/|___| |_| |___/ |_| |_|_\___/_/ \_\_|  |_| 
INFO[2023-06-20T21:00:54-07:00]                                              
INFO[2023-06-20T21:00:54-07:00] https://docs.nats.io/jetstream               
INFO[2023-06-20T21:00:54-07:00]                                          

[bruth]

Thanks @renevo. LGTM, but will let the server team chime. Can you rebase it against the dev branch (targeting 2.10)?

[ripienaar]

LGTM

[derekcollison]

LGTM