{Core} Make CLI respect file logging configuration option: enable_log_file and AZURE_LOGGING_ENABLE_LOG_FILE env variable

[haroldrandom]

Description of PR (Mandatory)
I am migrating test framwork from nose to pytest and found CLI would log every command's invocation output to a filep even though I configured in ~/.azure/config

[logging]
enable_log_file = no

And consequently, pytest wouldn't clear the AzCLI instance cleanly such that the test process would crash because of holding too many file descriptor (over the limit by OS):

So, here, I want to enable the ability to repect the logging configuratin even though I won't use it in CI. I will fire another PR to fix the bug that CLI holding too many opened files. (related issues: #12882, #10435)

Testing Guide
It affects two instance variables' assignment command_logger_handler and command_metadata_logger.
In the places they are referenced, there is a fault protection, so, it won't be a problem if user disbale the output of a logger to a log file.

Verify by running command with prefix AZURE_LOGGING_ENABLE_LOG_FILE=no or config in ~/.azure/config like above, then there should be no files under ~/.azure/commands/. Otherwise, there should be a file under that folder

History Notes:
(Fill in the following template if multiple notes are needed, otherwise PR title will be used for history note.)

[Component Name 1] (BREAKING CHANGE:) (az command:) make some customer-facing change.
[Component Name 2] (BREAKING CHANGE:) (az command:) make some customer-facing change.

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[yonzhan]

pytest

[fengzhou-msft]

The default for logging is no in az configure.

[fengzhou-msft]

However, changing it to no could be a breaking change since the bug made the actual default to be logging enabled.

[haroldrandom]

I overwrite the implementation from knack to enable logging by default like currenty CLI does, so it's transparency to user. Not a breaking it is.

[jiasli]

FYI, Knack handles the logging correctly:

https://github.com/microsoft/knack/blob/master/knack/log.py#L129-L131

        if self.file_log_enabled:
            self._init_logfile_handlers(root_logger, cli_logger)
            get_logger(__name__).debug("File logging enabled - writing logs to '%s'.", self.log_dir)