refactor: introduce enum class for MnType and clean up implementation accordingly

[knst]

Issue being fixed or feature implemented

expressions like nType == MnType::HighPerformance.index look pretty confusing in current implementation of 4k HPMN.

Changing uint8_t index to enum class MnType : uint8_t give pros:

• switch inside GetMnType() and any similar code will show a compiler warning if any type is missing.
• instead "MnType::HighPerformance.index" you can write MnType::HighPerformance
• you can remove confusing .index from MnType

But also Cons:

• instead log("%d", nType) you need to write log("%d", static_cast<int>(nType));

What was done?

Introduced new enum class MnType and rewritten generating Regular/HighPerformance objects with params (description, collateral amount, etc).

Also were added attributes [[no_discard]] for related code.

How Has This Been Tested?

Run unit/functional tests

Breaking Changes

No breaking changes.

Checklist:

• I have performed a self-review of my own code
• I have assigned this pull request to a milestone

[ogabrielides]

LGTM.

[UdjinM6]

LGTM, one nit

[UdjinM6]

LGTM, utACK

[ogabrielides]

LGTM, utACK