Remove EnableAuth parameter to configure the authentication

[mendaomn]

Description

This PR removes the possibility of disabling the authentication by changing a CloudFormation parameter.

In order to protect customers from affecting the security of their installation, this PR also removes the possibility of disabling the authentication by changing an environment variable passed to the Lambda

Changes

• remove EnableAuth CloudFormation parameter
• remove ENABLE_AUTH environment variable

How Has This Been Tested?

• ran unit and e2e tests
• set the environment variable and checked that the auth does not get disabled
• tested that you can still disable authentication when developing locally
• verified the Stack Create screen does not allow to configure the EnableAuth anymore (see screenshot below)
• set the environment variable in the Lambda Console and checked that auth does not get disabled

PR Quality Checklist

• [ ] I added tests to new or existing code
• [ ] I removed hardcoded strings and used our i18n solution instead (see here)
• [ ] I made sure no sensitive info gets logged at any time in the codebase (see here) (e.g. no user info or details, no stacktraces, etc.)
• [x] I checked that infrastructure/update_infrastructure.sh runs without any error
• [x] I checked that npm run build builds without any error
• [x] I checked that clusters are listed correctly
• [ ] I checked that a new cluster can be created (config is produced and dry run passes)
• [x] I checked that login and logout work as expected

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