feat: several fixes for Mailu 2024.06 support

[fastlorenzo]

Several fixes are introduces in order to support correctly Mailu 2024.06:

• Adding the option to set AUTH_REQUIRE_TOKENS env var via authRequireTokens
• Fixed healthcheck in front pod
• Fixed ingress to use HTTPS to connect to the front pod (and enabled 443/tcp port in front service to support this)
• Added the option to configure the PROXY_PROTOCOL en var via ingress.proxyProtocol
• Disabled submission port by default (in line with new Mailu behavior)
• Added the option to expose ManageSieve to the front-external service via front.externalService.manageSieve
• Setting the PORTS env var via what's configured in front.externalService + ports 80/443 if ingress.enabled is set