add support multiple services and notifications for macOS(darwin)

[nobonobo]

#54 fix

Add support multiple services and notifications for macOS.

Reason:

DeviceService-Value has a pointer for "cache of characteristics". DeviceService-Value argument is a duplicated value. So this cache pointer diverges before and after calling the DiscoverCharacteristics method.

https://github.com/tinygo-org/bluetooth/pull/56/files#diff-ab073822f13f923ebae9d8ec0e06899ef263c615fb9d27794634260744015bb9L90-L91

Changes:

• DeviceService rename to deviceService and wrapped DeviceService{*deviceService}
• DeviceService has charactaristics-cache.