Add bcrypt hashes support to basic_auth filter

Currently the auth_basic filter only supports SHA hashed passwords.

ExternalSecrets provide a htpasswd templating function from sprig that generates only bcrypt hashes

Supporting brcypt hashes for basic_auth will improve security and simplify the workflow I use -> `hashicorp vault>external secret>k8s secret>envoy gateway securitypolicy>envoy basic_auth filter`

https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/basic_auth_filter#configuration
https://masterminds.github.io/sprig/crypto.html
https://external-secrets.io/latest/guides/templating/