Revert when asset does not have decimals

[trmid]

This is to ensure a consistent UX. Assets without decimals() are very rare, and there are varying standards for what the default decimals should be (some apps fallback to 0, some fallback to 18), so if someone wants to deploy a new PrizeVault with an asset that has no specified decimals, they should create a custom deployment that uses the most applicable decimal value for the asset.

[linear]

GEN-1223 [M-172] Assets without decimals can cause UX issues

[github-actions]

LCOV of commit 3556d22 during coverage #510

Summary coverage rate:
  lines......: 99.5% (208 of 209 lines)
  functions..: 100.0% (55 of 55 functions)
  branches...: no data found

Files changed coverage rate:
                              |Lines       |Functions  |Branches    
  Filename                    |Rate     Num|Rate    Num|Rate     Num
  ==================================================================
  src/PrizeVault.sol          |99.4%    179| 100%    44|    -      0