Module is not using overridden ro_api_key / rw_api_key

Problem/Motivation

I want to use ENV variables to store API Keys to avoid putting those to the git repo.

Steps to reproduce

Use settings.php to override API Keys, like such:

// Set Typesense keys from env vars if available.
$typesense_read_key = getenv('TYPESENSE_READ_KEY');
$typesense_api_key = getenv('TYPESENSE_API_KEY');
if ($typesense_read_key) {
  $config['search_api.server.typesense_server']['backend_config']['ro_api_key'] = $typesense_read_key;
}
if ($typesense_api_key) {
  $config['search_api.server.typesense_server']['backend_config']['rw_api_key'] = $typesense_api_key;
}

This can be verified to work by doing `drush cget search_api.server.typesense_server --include-overridden`

But this module is using the non-overriden version of API keys in some places. I'm unable to deploy this server from configuration to staging environment because it is telling me that API key is missing.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes