Fix memory leak in clients/horizonclient/client.go:166 - stream

[vxxvvxxv]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  services/friendbot, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated any docs (developer docs, .md
  files, etc... affected by this change). Take a look in the docs folder for a given service,
  like this one.

Release planning

• I've reviewed the changes in this PR and if I consider them worthwhile for being mentioned on release notes then I have updated the relevant CHANGELOG.md within the component folder structure. For example, if I changed horizon, then I updated (services/horizon/CHANGELOG.md. I add a new line item describing the change and reference to this PR. If I don't update a CHANGELOG, I acknowledge this PR's change may not be mentioned in future release notes.
• I've decided if this PR requires a new major/minor version according to
  semver, or if it's mainly a patch change. The PR is targeted at the next
  release branch if it's not a patch change.

What

A memory leak has been detected in the steam function in file clients/horizonclient/client.go:166 (link). This behavior was discovered when attempting to use a non-existent address. The issue is that resp.Close is called after checking the resp.Status.

Why

As a test, I used 4000 non-existent addresses and the allocated memory started to grow rapidly (bytes.growSlice). Below, I provide a comparison through pprof/heap before and after my changes.

Before:

File: ___cursors
Build ID: cdd21ff2deb667b43aacc7fac45d96da8d08bfe2
Type: inuse_space
Time: 2025-07-09 16:56:12 +05
Entering interactive mode (type "help" for commands, "o" for options)
(pprof) top
Showing nodes accounting for 413.45MB, 79.39% of 520.80MB total
Dropped 131 nodes (cum <= 2.60MB)
Showing top 10 nodes out of 98
      flat  flat%   sum%        cum   cum%
  149.23MB 28.65% 28.65%   149.23MB 28.65%  bytes.growSlice
   72.78MB 13.97% 42.63%    72.78MB 13.97%  bufio.NewReaderSize (inline)
   67.26MB 12.92% 55.54%    67.26MB 12.92%  bufio.NewWriterSize (inline)
   28.01MB  5.38% 60.92%    28.01MB  5.38%  runtime.malg
   24.02MB  4.61% 65.53%    24.02MB  4.61%  crypto/internal/fips140/aes/gcm.NewGCMForTLS12
      17MB  3.26% 68.80%   194.06MB 37.26%  net/http.(*Transport).dialConn
   16.50MB  3.17% 71.97%    16.50MB  3.17%  net/textproto.MIMEHeader.Set
   16.01MB  3.07% 75.04%    16.01MB  3.07%  crypto/tls.Client (inline)
   12.56MB  2.41% 77.45%    12.56MB  2.41%  sync.(*Pool).pinSlow
   10.08MB  1.94% 79.39%    10.08MB  1.94%  crypto/internal/fips140/mlkem.NewDecapsulationKey768

After:

File: ___cursors
Build ID: 124c76d253b380d966a33f1b0c4ed666bd15dbb8
Type: inuse_space
Time: 2025-07-09 17:02:16 +05
Entering interactive mode (type "help" for commands, "o" for options)
(pprof) top
Showing nodes accounting for 32.54MB, 76.25% of 42.68MB total
Showing top 10 nodes out of 119
      flat  flat%   sum%        cum   cum%
   12.01MB 28.13% 28.13%    12.01MB 28.13%  runtime.malg
   10.02MB 23.48% 51.61%    10.02MB 23.48%  runtime.allocm
    2.01MB  4.71% 56.32%     2.01MB  4.71%  sync.(*Pool).pinSlow
    1.50MB  3.52% 59.83%     1.50MB  3.52%  github.com/sirupsen/logrus.New
    1.50MB  3.52% 63.35%     1.50MB  3.52%  net.(*Resolver).lookupIPAddr
    1.50MB  3.52% 66.86%        2MB  4.69%  context.withCancel (inline)
       1MB  2.35% 69.22%        1MB  2.35%  bytes.growSlice
       1MB  2.34% 71.56%        1MB  2.34%  main.main.WithFields.func3
       1MB  2.34% 73.90%     1.50MB  3.52%  context.(*cancelCtx).Done
       1MB  2.34% 76.25%        4MB  9.37%  private_repository/***/cursors.(*Service).ListenAndServeStellarPayments