CHAINS-6848 Merge upstream/master for btc testnet4 changes

[rahul-aravind-opti]

Steps:

git remote add upstream https://github.com/btcsuite/btcd.git
git remote -v
git checkout -b fetch-upstream-11-10-2025
git fetch upstream
git merge upstream/master

Fixed the merge conflicts with claude

 1. .gitignore: Kept both the Goland .idea entry and added the new .DS_Store and .aider* entries from upstream
  2. rpcclient/infrastructure.go: Merged both changes by:
    - Keeping the ParseAddressString logic from upstream for Unix socket support
    - Keeping the ObservingTransport wrapper from your branch for response capture
    - Keeping the defaultHTTPTimeout from upstream

Update(.gitignore)
  ⎿  Updated .gitignore with 1 addition and 3 removals
       56    /findcheckpoint
       57    /gencerts
       58
       59 -  <<<<<<< HEAD
       59    #Goland
       60    .idea
       61 -  =======
       61 +
       62    .DS_Store
       63    .aider*
       64 -  >>>>>>> upstream/master

⏺ Update(rpcclient/infrastructure.go)
  ⎿  Updated rpcclient/infrastructure.go with 4 additions and 11 removals
       1373        }
       1374      }
       1375
       1376 -  <<<<<<< HEAD
       1377 -    transport := &ObservingTransport{
       1378 -      Base: &http.Transport{
       1379 -  =======
       1376      parsedDialAddr, err := ParseAddressString(config.Host)
       1377      if err != nil {
       1378        return nil, err
       1379      }
       1380 -    client := http.Client{
       1381 -      Transport: &http.Transport{
       1382 -  >>>>>>> upstream/master
       1380 +
       1381 +    transport := &ObservingTransport{
       1382 +      Base: &http.Transport{
       1383          Proxy:           proxyFunc,
       1384          TLSClientConfig: tlsConfig,
       1385          DialContext: func(ctx context.Context, _,
     ...
       1396            )
       1397          },
       1398        },
       1399 -  <<<<<<< HEAD
       1399        // Wrap with response capturing if callback provided
       1400        OnResponseCapture: config.OnResponseCapture,
       1401      }
       1402
       1403      client := http.Client{
       1404        Transport: transport,
       1405 -  =======
       1406 -      Timeout: defaultHTTPTimeout,
       1407 -  >>>>>>> upstream/master
       1405 +      Timeout:   defaultHTTPTimeout,
       1406      }
       1407
       1408      return &client, nil