* Add session context outbounds as slice
slice is needed for dialer proxy where two outbounds work on top of each other
There are two sets of target addr for example
It also enable Xtls to correctly do splice copy by checking both outbounds are ready to do direct copy
* Fill outbound tag info
* Splice now checks capalibility from all outbounds
* Fix unit tests
* chore: fix some errors detected by staticcheck
* feat: remove `rand.Seed()` usage for possibly using "fastrand64" runtime to avoid locking
ref: https://pkg.go.dev/math/rand#Seed
- Add outbound name
- Add outbound conn in ctx
- Refactor splice: it can be turn on from all inbounds and outbounds
- Refactor splice: Add splice copy to vless inbound
- Fix http error test
- Add freedom splice toggle via env var
- Populate outbound obj in context
- Use CanSpliceCopy to mark a connection
- Turn off splice by default
* Increase some tls test timeout
* Fix TestUserValidator
* Change all tests to VMessAEAD
Old VMess MD5 tests will be rejected and fail in 2022
* Chore: auto format code
