Mention that statements should be prepared only once, then executed multiple times

[wprzytula]

A user shared a following doubt:

About using prepare statements in rust driver:

1. Run prepare once and hold the result in some variable or static. Then we use this variable for every execute.
2. Run the prepare statement every time before we execute based on it.

I wonder which way is better. As prepare statements has to deal with nodes and caches, I'm not getting useful information from rust driver documentation.

My quick check confirms that the documentation indeed lacks clear information about this. Let's have it spelled out that the first option is preferred.