avoid creating duplicate stack traces

[gregwebs]

This is done by using the new AddStack function instead of WithStack.
There is also a StackError utility function exposed.

[lysu]

Hi @gregwebs , we need make a decisioin how to identity duplicate stack~?

there will be much AddStack call in TiDB before we remove middle used call(near every level), IMHO, bottom-up mark hasStack flag make higher cost than recurse call GetStackTracer(although pingcap/tidb@3712fc1 make more modification)~ 😆 ?

[lysu]

expect that, we meet other problem, tidb has too many pending PR and we prefer rename some method name of pkg/errors to decrease old code modification.

e.g.

AddStack ==> Trace
Wrap ==> Annotate
Wrapf ==> Annotatef

can we do them in this repo, how do you think abouth it~? 🐱

[gregwebs]

Sounds good. Addressed in this PR: https://github.com/lysu/errors/pull/2