make oasis-net-runner default fixtures more useful

[matevz]

This PR makes oasis-net-runner defaults more tailored to local (dApp) development and debugging:

• increases balance of test account to 10^15 base units (1 million TEST)
• sets max_allowances to 16 in order to make deposits to runtimes possible without passing a separate staking genesis fixture

Related oasis-sdk PR: oasisprotocol/oasis-sdk#1081

[codecov]

Codecov Report

Merging #4902 (48ead79) into master (7fa7883) will increase coverage by 0.06%.
The diff coverage is 0.00%.

❗ Current head 48ead79 differs from pull request most recent head 71aed06. Consider uploading reports for the commit 71aed06 to get more accurate results

@@            Coverage Diff             @@
##           master    #4902      +/-   ##
==========================================
+ Coverage   66.60%   66.66%   +0.06%     
==========================================
  Files         464      464              
  Lines       50977    50977              
==========================================
+ Hits        33954    33986      +32     
+ Misses      12833    12815      -18     
+ Partials     4190     4176      -14     

Impacted Files	Coverage Δ
go/oasis-node/cmd/common/genesis/staking.go	69.86% <0.00%> (ø)
go/consensus/tendermint/apps/staking/auth.go	62.96% <0.00%> (-14.82%)	⬇️
go/common/grpc/auth/auth.go	94.73% <0.00%> (-5.27%)	⬇️
go/sentry/api/grpc.go	40.62% <0.00%> (-3.13%)	⬇️
go/common/logging/zap.go	62.58% <0.00%> (-2.88%)	⬇️
go/oasis-node/cmd/ias/auth_registry.go	65.81% <0.00%> (-2.57%)	⬇️
go/runtime/host/multi/multi.go	70.58% <0.00%> (-2.21%)	⬇️
go/consensus/api/submission.go	60.86% <0.00%> (-2.18%)	⬇️
go/storage/mkvs/lookup.go	77.08% <0.00%> (-2.09%)	⬇️
go/oasis-node/cmd/stake/delegations.go	78.99% <0.00%> (-1.69%)	⬇️
... and 32 more

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