Fixed "vttablet --help" to show correct command line flags

[rasikakale]

I fixed the vttablet --help error which gave flags that were not operable for other apps by doing the following fixes:

• Created testhandler and staticauthserver package within mysql package

• testhandler contains the following files that I moved from mysql into this package:
  - conn_test.go
  - query_test.go
  - replication_test.go
  - testhandler.go (contains TestHandler type originally part of mysql/query_benchmark_test.go)

• staticauthserver contains the following files also moved from mysql into this package:
  - auth_server_static_test.go
  - auth_server_static.go

• These files were moved from the mysql package to the endtoend package:
  - handshake_test.go
  - server_test.go
  - auth_server_clientcert_test.go

• static_user_data.go file added to the mysql package that contains the StaticUserData type originally in staticauthserver/auth_server_static.go

• I added prefixes of the appropriate package name in front of functions that are called outside of the package they are located in
  - e.g. A function RegisterAuthServerImpl() is defined in mysql/auth_server.go but called in staticauthserver/auth_server_static.go. The appropriate fix would be mysql.RegisterAuthServerImpl()

fixes: vitessio#4932

Signed-off-by: Rasika Kale rasika@planetscale.com