Remove dependency on tlscfg.Options

[yurishkuro]

In a series of PRs for #4316 we removed the dependency on tlscfg.Options producing tls.Config by replacing it with the corresponding OTEL functions (PR #6345).

We can clean this up even further and make Options struct to be private in tlscfg, by changing the signature of ServerFlagsConfig.InitFromViper and ClientFlagsConfig.InitFromViper to return the corresponding OTEL structs directly, rather than returning Options, because every time we call those functions we immediately call ToOtelServerConfig() on the returned value, for example

jaeger/cmd/collector/app/flags/flags.go

Lines 211 to 215 in 08a2bff

	tlsOpts, err := cfg.tls.InitFromViper(v)
	if err != nil {
	return fmt.Errorf("failed to parse GRPC TLS options: %w", err)
	}
	opts.TLSSetting = tlsOpts.ToOtelServerConfig()

Sample change:

-func (c ServerFlagsConfig) InitFromViper(v *viper.Viper) (Options, error) {
+func (c ServerFlagsConfig) InitFromViper(v *viper.Viper) (*configtls.ServerConfig, error) {
        var p Options
        p.Enabled = v.GetBool(c.Prefix + tlsEnabled)
        p.CertPath = v.GetString(c.Prefix + tlsCert)
@@ -99,11 +100,11 @@ func (c ServerFlagsConfig) InitFromViper(v *viper.Viper) (Options, error) {
        if !p.Enabled {
                var empty Options
                if !reflect.DeepEqual(&p, &empty) {
-                       return p, fmt.Errorf("%s.tls.* options cannot be used when %s is false", c.Prefix, c.Prefix+tlsEnabled)
+                       return nil, fmt.Errorf("%s.tls.* options cannot be used when %s is false", c.Prefix, c.Prefix+tlsEnabled)
                }
        }

-       return p, nil
+       return p.ToOtelServerConfig(), nil
 }

We should also remove mapstructure tags from the Options struct, since we're not using it in the config files.

[120EE0980]

I want to take up this issue if its not urgent as I am still exploring and understanding codebase .