[Enhancement] Refactor Starter Species to use separate EggTier map

[ben-lear]

What are the changes the user will see?

No functional changes.

Why am I making these changes?

Creates a new Species EggTier map that can be used by Balance team to set EggTier separately from a species' starter cost. Allows for situations like Regice, where it is still obtainable from Epic eggs as a sub-legendary but has starter cost of 5, etc.

What are the changes from a developer perspective?

Not much changes, except an egg calculates its EggTier from the speciesEggTier map now instead of from speciesStarterCosts.

Also removed a redundant math clamping function in utils.ts

How to test the changes?

Eggs are hatching with normal expected species. There are no balance changes in this PR.

Checklist

• I'm using beta as my base branch
• There is no overlap with another PR?
• The PR is self-contained and cannot be split into smaller PRs?
• Have I provided a clear explanation of the changes?
• Have I considered writing automated tests for the issue?
• If I have text, did I make it translatable and add a key in the English locale file(s)?
• Have I tested the changes (manually)?
  • Are all unit tests still passing? (npm run test)
• Are the changes visual?
  • Have I provided screenshots/videos of the changes?

[torranx]

lgtm