main/ell: upgrade to 0.21

cherry-pick fix-out-of-bounds-access from development branch
cherry-pick T1-timeout-crash from development branch
1 job for !30 with ell-0.21 in 18 seconds (queued for 3 seconds)
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Status Job ID Name Coverage
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failed #379
docker-alpine x86_64 allowed to fail
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00:00:18

 
Name Stage Failure
failed
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