P-chain - introducing fees calculators

[abi87]

Why this should be merged

This PR introduced fees.Calculator which will calculate fees associated with a given transaction. fees.Calculator is pretty simple pre E upgrade, but will be upgraded in next PRs to meter tx complexity (across multiple fee dimensions) once E upgrade activates.

How this works

• Pull all static config to fee package where fee.Calculator is defined
• Introduce the static fee calculator
• Added unit tests to check static fees applied in different forks (which is the main reason the the LOC of this PR)

How this was tested

CI