Prepare benchmarks for memory streams

[MauriceVanVeen]

Benchmarks like BenchmarkJetStreamPublish would fail when changed to use memory-based storage with the following message:

BenchmarkJetStreamPublish/N=3,R=3,MsgSz=1024b,Subjs=1/Async[W:4000]
    jetstream_benchmark_test.go:738: Publish timed out

This was due to the underlying error being hit:

Apply stream entries for '$G > S' got error processing message: insufficient resources (10023)

Making the maximums consistent so all file-based benchmarks/tests can also run for memory-based without timing out due to insufficient resources.

Signed-off-by: Maurice van Veen github@mauricevanveen.com

[wallyqs]

LGTM