Timing Rust examples in release mode

[Paul Sanders]

Currently the Rust bench marks are taken in debug mode, ie:

cargo run -- 1000

Running in release mode will optimize the program to be faster and give a better idea of the numbers people would see in a released program.

cargo run -r -- 1000

[Prashanth Rao]

I'd done this for the mock_data generation piece, but forgot to do it for this one. Will make the updates to the docs too and close this once it's done 👍🏽

[Prashanth Rao]

Will address this once we are able to address the 1M async data load in sqlx.