[runtime] Use coop handles for some simple icalls

[runtime] Use coop handles for some simple icalls

- System.Text.EncodingHelper.InternalCodePage
- System.Runtime.InteropServices.Marshal.PtrToStringAnsi(intptr)
- Use coop handles for ves_icall_System_Configuration_DefaultConfig_get_machine_config_path
- Use coop handles for ves_icall_System_Configuration_InternalConfigurationHost_get_bundled_app_config
- Use coop handles for System.Web.Util.ICalls.GetMachineInstallDirectory