*: use pingcap/log (zap) for logging

[kennytm]

What problem does this PR solve?

Switch to use the uniform log format.

What is changed and how it works?

The log library is changed from logrus to zap, a structured logger.

Due to how structured logging usually works, several interfaces are rewritten.

• Child loggers are heavily used to abstract away contextual information in the log, e.g. the table name, engine UUID etc. Many types which originally compute these tagging information on-line are changed to storing a child logger instead.
• The 3 functions QueryRowWithRetry/TransactWithRetry/ExecWithRetry originally writes log without any contextual information. These are modified to accept a logger. The common arguments are abstracted into an SQLWithRetry type.

All logging infrastructures (e.g. common.AppLogger) are moved from common into a new log package.

• Like common.AppLogger, we need to define our own logger log.L() distinct from the true global one "github.com/pingcap/log".L() so we could control TiDB's logging level independently (though perhaps we could investigate whether merging the two is possible nowadays).
• Stack traces of error level logs are entirely disabled, and stack traces of errors are by default inhibited by the log.ShortError function, to avoid flooding the log with noise.
• A common pattern used in Lightning is:
  1. Log that a task has started
  2. Perform a task
  3. Log that a task has ended, and display the total time taken.
     This is codified into the log.Task type.

Several redundant error logs are eliminated (e.g. if f() calls g() calls h(), and h() logs an error, then g() and f() will not log the error again).

Following pingcap/tidb#10025's lead, when refactoring a function, if an error is known to be a custom error, errors.Trace will no longer be applied. This will be done more thoroughly in the future, after unit-test coverage is improved.

Check List

Tests

• Unit test
• Integration test

Side effects

• Breaking backward compatibility
  • Log format is modified

Related changes

• Need to update the documentation

[kennytm]

/run-all-tests tidb=master tikv=master pd=master

[kennytm]

Output looks like:

[kennytm]

/run-all-tests

[IANTHEREAL]

@july2993 @lonng PTAL

[csuzhangxc]

LGTM

[july2993]

rest LGTM

[lonng]

Rest LGTM

[kennytm]

/run-all-tests

[july2993]

LGTM