Fix so that HTTP request don't wait for responses indefinitely

[torao]

Description

Currently, there are a few codes that use the golang http.Client with no timeout in Ostracon. This can cause stability and safety problems for nodes, as they behave as that they are waiting indefinitely when the destination doesn't respond.

This PR replaces HTTP requests naively used without timeouts with those with timeouts. However, this is only for code related to http.Client{} or related http.Get(), and doesn't consider other TCP or Unix communications.

This fix sets the timeout as follows:

• If it has a general idea of what timeout to expect, apply it.
• Apply 30 seconds for requests used in UPnP. It's sufficient for a human to actually enter the command and ensure that UPnP is not working.
• Apply 60 seconds for requests used in testing. This is because the load in a CI environment can cause even correct behavior to take a significant amount of time to respond.
• Do nothing for use cases where callers are using with and without timeouts, i.e., explicitly expecting no timeout.

The only places affected other than the test code are the CLI commands UPnP prove→discover and dump.

[codecov]

Codecov Report

Merging #506 (f690d36) into main (e6f57a1) will increase coverage by 0.04%.
The diff coverage is 91.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #506      +/-   ##
==========================================
+ Coverage   65.39%   65.44%   +0.04%     
==========================================
  Files         278      279       +1     
  Lines       37995    37984      -11     
==========================================
+ Hits        24846    24857      +11     
+ Misses      11328    11314      -14     
+ Partials     1821     1813       -8     

Impacted Files	Coverage Δ
rpc/jsonrpc/client/test_util.go	0.00% <0.00%> (ø)
libs/net/http.go	100.00% <100.00%> (ø)
crypto/sr25519/pubkey.go	35.89% <0.00%> (-7.70%)	⬇️
blockchain/v2/routine.go	63.91% <0.00%> (-5.16%)	⬇️
abci/client/socket_client.go	72.09% <0.00%> (-0.88%)	⬇️
blockchain/v2/reactor.go	34.71% <0.00%> (-0.30%)	⬇️
p2p/conn/connection.go	79.80% <0.00%> (-0.20%)	⬇️
proxy/multi_app_conn.go	47.66% <0.00%> (ø)
crypto/vrf/vrf_libsodium.go
crypto/vrf/vrf_r2ishiguro.go	100.00% <0.00%> (ø)
... and 9 more