refactor(core-p2p): don't test private methods in the peer guard

[faustbrian]

Proposed changes

Marks the determine* methods of the peer guard as private and adjusts tests to only test the public API.

Types of changes

• Refactoring (improve a current implementation without adding a new feature or fixing a bug)

Checklist

• I have read the CONTRIBUTING documentation
• Lint and unit tests pass locally with my changes

[codecov-io]

Codecov Report

Merging #2359 into 2.4 will not change coverage.
The diff coverage is 81.81%.

@@           Coverage Diff           @@
##              2.4    #2359   +/-   ##
=======================================
  Coverage   66.47%   66.47%           
=======================================
  Files         400      399    -1     
  Lines        8535     8535           
  Branches      375      375           
=======================================
  Hits         5674     5674           
  Misses       2818     2818           
  Partials       43       43

Impacted Files	Coverage Δ
packages/core-p2p/src/monitor.ts	66.8% <100%> (ø)	⬆️
packages/core-p2p/src/peer.ts	40.35% <100%> (ø)	⬆️
packages/core-p2p/src/guard.ts	75% <80%> (ø)

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