Persist CLI connection credentials

[jasanpe]

Summary

• persist optional bearer token, TLS certificate path, and TLS certificate key path in the active profile config
• use stored auth/TLS values when constructing the Permify gRPC client
• collect the optional connection credentials during permctl configure before listing tenants
• write the config file with owner-only permissions

Fixes #2

Tests

• go test ./...
• go vet ./...

/claim #2