Prevents line breaks in delivery service remapText field (UI and API) (#4305) (#4317)

* prevents line breaks in ds.remapText (UI and API)

* adds test to ensure ds.remapText cannot include a line break

* updated fixtures to include valid line breaks for edge/mid header rewrites, regex remap and tr request/response headers

* adds period to GoDoc

* no need for ng-pattern

* textarea does not support pattern so switching back to ng-pattern

(cherry picked from commit c025d2297168fc46d4fd4a9693aad9161bdc0015)
7 files changed