Increase scheduler max batch size

[nhynes]

The value of 16M was taken from the the CLI flags

[codecov]

Codecov Report

Merging #2741 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2741      +/-   ##
==========================================
- Coverage   62.99%   62.96%   -0.03%     
==========================================
  Files         383      383              
  Lines       36094    36094              
==========================================
- Hits        22737    22728       -9     
- Misses      10495    10500       +5     
- Partials     2862     2866       +4

Impacted Files	Coverage Δ
go/worker/compute/executor/committee/state.go	74.07% <0%> (-25.93%)	⬇️
...ompute/txnscheduler/algorithm/batching/batching.go	78.66% <0%> (-6.67%)	⬇️
go/common/cbor/codec.go	64.7% <0%> (-5.89%)	⬇️
go/worker/compute/executor/committee/node.go	62% <0%> (-5.32%)	⬇️
.../consensus/tendermint/apps/epochtime_mock/state.go	84.61% <0%> (-5.13%)	⬇️
go/storage/metrics.go	75.21% <0%> (-5.13%)	⬇️
go/runtime/tagindexer/tagindexer.go	68.47% <0%> (-4.35%)	⬇️
go/consensus/tendermint/roothash/roothash.go	68.91% <0%> (-2.63%)	⬇️
go/worker/compute/merge/committee/node.go	75.37% <0%> (-2.49%)	⬇️
go/storage/client/client.go	76.47% <0%> (-2.11%)	⬇️
... and 18 more

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[pro-wh]

@matevz, any argument for the current value of 1000?