Add feature to print line number

[pmnoxx]

Motivation

We have been using tracing for logging. However, one if it's major drawbacks is inability to display line numbers.
When looking at logs I noticed that we spend a huge portion of log to display the target, but the line number is not included,
making the log somewhat useless.

I often use tracing for debugging, and I would prefer to have line numbers written. As a user of log4j. I know how important line numbers are while debugging issues. It allows to quickly jump to the right line number to see the code, which printed the error, rather than having to search for it. Sometimes, it's not possible to uniquely determine which line logged given message, unless the user specifies it.

Solution

Add logging line numbers, for example:

2021-12-26T23:09:29.508100Z  INFO play_ground::anything:6: res=[1, 2, 4, 8, 16, 32]
2021-12-26T23:09:29.508135Z  INFO play_ground::anything:22: send=Err(Os { code: 89, kind: Uncategorized, message: "Destination address required" })

Previously, the message would be:

2021-12-26T23:09:29.508100Z  INFO play_ground::anything: res=[1, 2, 4, 8, 16, 32]
2021-12-26T23:09:29.508135Z  INFO play_ground::anything: send=Err(Os { code: 89, kind: Uncategorized, message: "Destination address required" })

Notes:

• line_numbers are only drawn when display_target is defined - can be extended to work without display_target - as a separate PR

Questions:

• added with_line_numbers test - what other tests do we need?
• should pretty still print line_numbers if this option is disabled?

[hawkw]

This seems like a duplicate of PR #1773, so we'll have to decide which one should be merged. I believe #1773 adds slightly more functionality (it also adds the option to display file paths...)