refactor: sequencer inbox DAS changes

[fredlacs]

Refactored a couple things:

• removed a calldata to memory copy when processing batches
• removed low level assembly syntax
• refactored batch data validation into a single modifier
• removed overflow validation step which isn't needed in solidity >= 0.8
• added a struct to track DAS keysets

[codecov]

Codecov Report

Merging #698 (77923a0) into refactor-accumulator-flow (b8f66e1) will decrease coverage by 4.54%.
The diff coverage is 38.88%.

@@                      Coverage Diff                      @@
##           refactor-accumulator-flow     #698      +/-   ##
=============================================================
- Coverage                      52.01%   47.47%   -4.55%     
=============================================================
  Files                            224      213      -11     
  Lines                          26727    22690    -4037     
  Branches                         495      493       -2     
=============================================================
- Hits                           13901    10771    -3130     
+ Misses                         11380    10473     -907     
  Partials                        1446     1446              

[PlasmaPower]

LGTM