fix(p2p/exchange): set timeout if it was not provided for Head request

[vgonkivs]

Overview

Setting a default timeout, if it wasn't set, allows us to avoid any cases when the Head request could stuck.

Checklist

• New and updated code has appropriate documentation
• New and updated code has new and/or updated testing
• Required CI checks are passing
• Visual proof for any user facing features like CLI or documentation updates
• Linked issues closed with keywords

[Wondertan]

There should be a way for the caller to wait indefinitely until it gets the result(especially when #149 gets implemented). The caller decides whether he wants a deadline or not. This solution limits that by always setting a deadline. Instead, we should set a deadline on the caller side which is in sync_head.go where we request recent head if we have outdated. In that case its also acceptable to ignore context timeout error and proceed with outdated header we have

[vgonkivs]

I have only one concern: we can request head from non-trusted peers, which means we don't guarantee that this particular peer will work as expected. Also, there is no punishment in the case when a peer does not respond at all and simply blocks the request. This malicious peer can hold 1-5-10-20 requests, so a lot of other "callers" will be blocked indefinitely.

It also won't be fixed when #149 is done because we can have 2-3 malicious peers in the peer tracker.

So, on the one hand, I agree with you that the caller should have the ability to not specify a timeout but from the other side, we are requesting 1 header that could not take more than even a minute + we are not requesting a particular height(which the node does not have). Every node has its own head and should serve it once it receives the request

[renaynay]

isn't this still too long?

[vgonkivs]

I'm ok with setting even 1-2 seconds

[vgonkivs]

closed in favour of #152