Add StartConfig.Listener so server with custom Listener is easier to create

[aldas]

Add StartConfig.Listener so server with custom Listener is easier to create

relates to #2918 (comment)
#1942

Example:

package main

import (
	"context"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/labstack/echo/v5"
)

func main() {
	e := echo.New()

	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer cancel()

	lc := net.ListenConfig{
		KeepAlive: 15 * time.Second,
		//Control:   nil,
		//KeepAliveConfig: net.KeepAliveConfig{
		//	Enable:   false,
		//	Idle:     0,
		//	Interval: 0,
		//	Count:    0,
		//},
	}
	l, err := lc.Listen(ctx, "tcp", ":8080")
	if err != nil {
		e.Logger.Error("failed to create listener", "error", err)
		return
	}
	defer l.Close()

	sc := echo.StartConfig{
		Listener: l,
	}
	if err := sc.Start(ctx, e); err != nil {
		e.Logger.Error("failed to run server", "error", err)
	}
}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.01%. Comparing base (19364e2) to head (5571024).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2920   +/-   ##
=======================================
  Coverage   93.01%   93.01%           
=======================================
  Files          43       43           
  Lines        4496     4498    +2     
=======================================
+ Hits         4182     4184    +2     
  Misses        196      196           
  Partials      118      118           

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.