feat: refactor and improve HTTP server handling

[appleboy]

• Add type definitions for listenAndServe and cleanup in graceful.go
• Add appendHTTPServer function to Graceful struct in graceful.go
• Change appendHttpServer function to appendHTTPServer in graceful.go
• Add ReadHeaderTimeout field to http.Server struct in appendHTTPServer function in graceful.go
• Add tests for TestCycle, TestWithFd, TestWithContext, and TestRunFd functions in graceful_test.go
• Change variable names and function calls in TestCycle, TestWithFd, TestWithContext, and TestRunFd functions in graceful_test.go
• Add code for loading PEM file and creating certificate pool in testRequest function in graceful_test.go
• Change InsecureSkipVerify field to RootCAs and add MinVersion field in testRequest function in graceful_test.go
• Change variable names and function calls in testRequest function in graceful_test.go
• Change variable names and function calls in WithAddr and WithTLS functions in options.go
• Change variable names and function calls in listen function in options.go
• Modify cert.pem and key.pem files in testdata/certificate directory

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (master@4a6271f). Click here to learn what that means.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff            @@
##             master       #9   +/-   ##
=========================================
  Coverage          ?   77.83%           
=========================================
  Files             ?        2           
  Lines             ?      212           
  Branches          ?        0           
=========================================
  Hits              ?      165           
  Misses            ?       32           
  Partials          ?       15           

Flag	Coverage Δ
go-	77.83% <0.00%> (?)
go-1.20	77.83% <0.00%> (?)
go-1.21	77.83% <0.00%> (?)
macos-latest	77.83% <0.00%> (?)
ubuntu-latest	77.83% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.