Add fork test and multicall

[trmid]

Also enforced alignment of promotion epochs with twab periods to avoid twab overwrite exploits.

[linear]

GEN-864 Add fork tests for TwabRewards on V5 Optimism

Test for multiple vaults, users, time frames, and reward tokens.

[github-actions]

LCOV of commit d13cbf5 during coverage #26

Summary coverage rate:
  lines......: 100.0% (106 of 106 lines)
  functions..: 100.0% (19 of 19 functions)
  branches...: no data found

Files changed coverage rate:
                     |Lines       |Functions  |Branches    
  Filename           |Rate     Num|Rate    Num|Rate     Num
  =========================================================
  src/TwabRewards.sol| 100%    106| 100%    19|    -      0