shred: assume fixed-32 fec sets

[emwang-jump]

No description provided.

[github-actions]

Performance Measurements ⏳

Suite	Baseline	New	Change
backtest mainnet-368528500-perf per slot	0.05061 s	0.050573 s	-0.073% ✅
backtest mainnet-368528500-perf snapshot load	1.633 s	1.642 s	0.551% ✅
backtest mainnet-368528500-perf total elapsed	50.609558 s	50.573484 s	-0.071% ✅
firedancer mem usage with mainnet.toml	1005.23 GiB	1005.23 GiB	0.000% ✅

[github-actions]

Performance Measurements ⏳

Suite	Baseline	New	Change
backtest mainnet-368528500-perf per slot	0.050643 s	0.050655 s	0.024% ✅
backtest mainnet-368528500-perf snapshot load	1.713 s	1.699 s	-0.817% ✅
backtest mainnet-368528500-perf total elapsed	50.642606 s	50.655248 s	0.025% ✅
firedancer mem usage with mainnet.toml	1005.23 GiB	1005.23 GiB	0.000% ✅

[ptaffet-jump]

Is there a reason to keep the shred34 struct? I think we should get rid of it, and simplify the structures

[emwang-jump]

Is there a reason to keep the shred34 struct? I think we should get rid of it, and simplify the structures

No good reason, just haven't gotten to it yet!