Display exact code block location when running doc-tests

[DelevoXDG]

Currently, the examples are just numbered:

            test hello_world::add (example 0) ... ok
            ...
            test hello_world::add (example 1) ... ok

We should instead aim to track and display the exact line of the code block in the source file, similar to rustdoc tests

running 4 tests
test src/lib.rs - divide (line 31) ... ignored
test src/lib.rs - add (line 12) ... FAILED
test src/lib.rs - add (line 18) ... FAILED
test src/lib.rs - add (line 6) ... ok

Continues #2473