Introduce first strategic provider: do nothing

[michaelavila]

These commits introduce an experimental provider system that, currently, does not provide. Functionality will be layered on to the experimental provider until it has all of the behavior needed to replace the default provider system.

The experimental system can be enabled by issuing the following command:

ipfs config Experimental.StrategicProviding true

Then you must restart your daemon.

[michaelavila]

@scout I think you'll find this PR useful. You mentioned to me not long ago that you'd like the ability to disable providing in IPFS without disabling content routing. This PR does exactly that. A series of upcoming PRs will flesh out the provider system further, but the ability to disable providing without disabling content routing itself will be preserved.

Is this something you can put to use right away? In its current form you'd need to set an experimental flag and restart the daemon. Will that work for what you have in mind?

[eefahy]

Thanks very much @michaelavila ! This will help a ton with debugging and observing bona-fide gateway traffic and save us some bandwidth costs to boot!

[magik6k]

I'll need to document some conventions used in the constructor after the refactors are done, the rest generally looks good.

[magik6k]

(also, more smaller commits would make reviewing easier)

All feedback addressed.

[magik6k]

LGTM (sorry for the delay, it somehow fell off my radar)

[michaelavila]

@magik6k no worries, thanks for following up!

[Stebalien]

🚀