Given that AccAddress is a []byte type, and its .String() method is
quite expensive, continuously invoking the method doesn't easily provide
a way for the result to be memoized. In memory profiles from
benchmarking OneBankSendTxPerBlock and run for a while, it showed >2GiB burnt
and SendCoins consuming a bunch of memory: >2GiB.
This change introduces a simple global cache with a map to intern
AccAddress values, so that we quickly look up the expensively computed
values. With it, the prior memory profiles are erased, and benchmarks
show improvements:
```shell
$ benchstat before.txt after.txt
name old time/op new time/op delta
OneBankSendTxPerBlock-8 1.94ms ± 9% 1.92ms ±11% -1.34% (p=0.011 n=58+57)
name old alloc/op new alloc/op delta
OneBankSendTxPerBlock-8 428kB ± 0% 365kB ± 0% -14.67% (p=0.000 n=58+54)
name old allocs/op new allocs/op delta
OneBankSendTxPerBlock-8 6.34k ± 0% 5.90k ± 0% -7.06% (p=0.000 n=58+57)
```
Fixes#8693
Co-authored-by: Alessio Treglia <alessio@tendermint.com>
Emmanuel T OdekeandAlessio Treglia
929b62cd46