Add Adapter::getContents & Adapter::putContents

[ghost]

This PR adds file read and write optimizations on the adapter level. Essentially it collapses open/read/close and open/write/close calls into one. Child Process is such an adapter which can use this optimization to reduce message passing & latency. Eio simulates the optimization by calling the necessary methods in sequence by itself.

Part of #46 & #46 (comment).

I want to add Eio has a very weird behaviour.

[clue]

@CharlotteDunois Thank you very much for this PR!

I agree that these methods make perfect sense from a consumer perspective and I agree that their naming makes sense in regards to the other methods. In the future, I would love to reconsider their naming in order to promote them more prominently

[ghost]

@clue If you have any specific naming in mind, speak your mind. If you can think of better names, it's better to change it now than later.

[WyriHaximus]

LGTM 👍

[WyriHaximus]

@clue ping

[ghost]

@clue Reminder. Also a reminder for buzz.

[ghost]

@clue @jsor @WyriHaximus I've got a new idea on how to expose "non-standardizable" feature. As such I've updated the PR and would need to be looked at again.

[clue]

@CharlotteDunois Thanks for the update, LGTM API-wise! 👍

What do you think about the below documentation suggestions?

[ghost]

@clue Updated!

[clue]

@CharlotteDunois Nice, thank you for the quick update, now let's get this shipped! 🎉

[WyriHaximus]

@CharlotteDunois could you squash both commits together? Will merge afterwards 👍