Support cors-allow-origin with multiple origins (#7614)

* Add Initial support for multiple cors origins in nginx

- bump cluster version for `make dev-env`
- add buildOriginRegex function in nginx.tmpl
- add e2e 4 e2e tests for cors.go
- refers to feature request #5496

* add tests + use search to identify '*' origin

* add tests + use search to identify '*' origin

Signed-off-by: Christopher Larivière <lariviere.c@gmail.com>

* fix "should enable cors test" looking at improper values

* Modify tests and add some logic for origin validation

- add origin validation in cors ingress annotations
- add extra tests to validate regex
- properly escape regex using "QuoteMeta"
- fix some copy/paste errors

* add TrimSpace and length validation before adding a new origin

* modify documentation for cors and remove dangling comment

* add support for optional port mapping on origin

* support single-level wildcard subdomains + tests

* Remove automatic `*` fonctionality from incorrect origins

- use []string instead of basic string to avoid reparsing in template.go
- fix typo in docs
- modify template to properly enable only if the whole block is enabled
- modify cors parsing
- test properly by validating that the value returned is the proper
  origin
- update unit tests and annotation tests

* Re-add `*` when no cors origins are supplied + fix tests

- fix e2e tests to allow for `*`
- re-add `*` to cors parsing if trimmed cors-allow-origin is empty
(supplied but empty) and if it wasn't supplied at all.

* remove unecessary logic for building cors origin + remove comments

- add some edge cases in e2e tests
- rework logic for building cors origin

there was no need for logic in template.go for buildCorsOriginRegex
if there is a `*` it ill be short-circuited by first if.

if it's a wildcard domain or any domain (without a wildcard), it MUST
match the main/cors.go regex format.

if there's a star in a wildcard domain, it must be replaced with
`[A-Za-z0-9]+`

* add missing check in e2e tests

build/dev-env.sh

@@ -61,7 +61,7 @@ echo "[dev-env] building image"
 make build image
 docker tag "${REGISTRY}/controller:${TAG}" "${DEV_IMAGE}"
 
-export K8S_VERSION=${K8S_VERSION:-v1.20.2@sha256:8f7ea6e7642c0da54f04a7ee10431549c0257315b3a634f6ef2fecaaedb19bab}
+export K8S_VERSION=${K8S_VERSION:-v1.21.1@sha256:69860bda5563ac81e3c0057d654b5253219618a22ec3a346306239bba8cfa1a6}
 
 KIND_CLUSTER_NAME="ingress-nginx-dev"