Add some enums for basic binding types.

[irvingos]

1. Add an enum type for basic binding types;
2. Modify the use of some primitive binding types to adapt to changes;

不妥之处，望指点！

[sofastack-bot[bot]]

Hi @IrvingOS, welcome to SOFAStack community, Please sign Contributor License Agreement!

After you signed CLA, we will automatically sync the status of this pull request in 3 minutes.

[OrezzerO]

@IrvingOS Thank you for your PR. Consider the situation that if I want to add a new binding type in my own project instead of sofaboot repo using the extensible ability of sofaboot and sofa-rpc. I can't inherit the enum class to create a new binding type.

[irvingos]

Therefore, I reserved BindingType and provided a method to convert from BindingTypeEnum to BindingType. If this is not feasible, how about providing some static constants? @OrezzerO

[HzjNeverStop]

这个改动会导致 API 不兼容，且降低了 type 的可扩展性，先关闭了。