Reduce datetime calls in peer discovery by factor of 100

[benaadams]

Changes

• Reduce calls to DateTime.UtcNow by factor of 100 (e.g. 3M -> 30k)
• After going through 1k peers for discovery wait TIME_WAIT before continuing to allow sockets to clear
• After going through all previously known peers for discovery wait TIME_WAIT before starting again to allow sockets to clear
• NetworkStorage: HashSet<PublicKey>+List<NetworkNode> -> Dictionary<PublicKey, NetworkNode>

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

[LukaszRozmej]

Can you provide some metrics or profiling how it affected peer management?

[benaadams]

Before (last column)

After