Memory/reduce allocations in peer manager

[LukaszRozmej]

Changes:

Reduce allocations in peer manager
More context: https://www.notion.so/nethermind/Memory-investigations-2aa0fa86988c4bf88849a66b7328f203#60e7fde6cfee4b5c9daa3e4b8507196f

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Other (please describe): memory fragmentation and performance

Testing

Requires testing

• Yes
• No

In case you checked yes, did you write tests??

• Yes
• No

[kkokosa]

Looks good to me. Reduces time 3x and allocations 4x:

|                  Method |       Mean |    Error |   StdDev |  Gen 0 | Allocated |
|------------------------ |-----------:|---------:|---------:|-------:|----------:|
| CleanupCandidatePeers_1 | 1,126.9 ns | 22.51 ns | 24.08 ns | 0.0992 |   1,664 B |
| CleanupCandidatePeers_2 |   406.7 ns |  6.85 ns |  6.41 ns | 0.0262 |     440 B

Allocations are from various places:

[tanishqjasoria]

Client instances seems to be running fine.

[LukaszRozmej]

Adding comments that help with review