fix: replace deprecated package io/ioutil with os or io

[ulbqb]

Description

Replace deprecated io/ioutil package since Go 1.16.

• ioutil.TempDir -> os.MkdirTemp
• ioutil.WriteFile -> os.WriteFile
• ioutil.ReadAll -> io.ReadAll
• ioutil.ReadFile -> os.ReadFile

[codecov]

Codecov Report

Merging #521 (7cd4349) into main (160e52f) will increase coverage by 0.07%.
The diff coverage is 71.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #521      +/-   ##
==========================================
+ Coverage   65.81%   65.88%   +0.07%     
==========================================
  Files         279      279              
  Lines       38057    38057              
==========================================
+ Hits        25047    25075      +28     
+ Misses      11209    11184      -25     
+ Partials     1801     1798       -3     

Impacted Files	Coverage Δ
libs/os/os.go	28.78% <0.00%> (ø)
rpc/jsonrpc/client/http_json_client.go	20.47% <0.00%> (ø)
rpc/jsonrpc/client/http_uri_client.go	0.00% <0.00%> (ø)
abci/example/kvstore/helpers.go	100.00% <100.00%> (ø)
config/toml.go	74.19% <100.00%> (ø)
consensus/state.go	73.99% <100.00%> (+0.75%)	⬆️
crypto/armor/armor.go	47.82% <100.00%> (ø)
libs/cli/helper.go	61.44% <100.00%> (ø)
p2p/key.go	67.24% <100.00%> (ø)
privval/file.go	74.90% <100.00%> (ø)
... and 18 more

[tnasu]

Thanks for your changes. I left the upstream PR. It's a far future work for us.

• do not use ioutil tendermint/tendermint#9206