feat: fix utils and add goroutine leak unit tests

[tarunKoyalwar]

Proposed changes

• add random user agent to fuzzing http requests ( by @Ice3man543 )
• detected goroutine leaks using leak tests
• added goroutine leak test as Unit test for nuclei sdk ( both SimpleNucleiExecuter & ThreadSafeNucleiExecuter )
• identified and fix number of known leaked goroutines
• based on use semaphore instead of deprecated resizablechannel utils#398

Note

test failure due to a minor issue in dependent utils pr , and should be fixed once it is resolved and merged

Great job by everyone involved 🎉

After fix

 go test -v ./... -count=1
=== RUN   TestSimpleNuclei
[INF] Templates clustered: 14 (Reduced 10 Requests)
[nameserver-fingerprint] scanme.sh
[caa-fingerprint] scanme.sh
{"duration":"0:00:01","errors":"1","hosts":"1","matched":"2","percent":"94","requests":"16","rps":"25","startedAt":"2024-04-29T21:41:57.866863+05:30","templates":"24","total":"17"}
--- PASS: TestSimpleNuclei (6.72s)
=== RUN   TestSimpleNucleiRemote
[nameserver-fingerprint] scanme.sh
--- PASS: TestSimpleNucleiRemote (4.38s)
=== RUN   TestThreadSafeNuclei
=== RUN   TestThreadSafeNuclei/scanme.sh
[INF] Templates clustered: 14 (Reduced 10 Requests)
[caa-fingerprint] scanme.sh
[nameserver-fingerprint] scanme.sh
=== RUN   TestThreadSafeNuclei/honey.scanme.sh
[INF] Templates clustered: 14 (Reduced 10 Requests)
[caa-fingerprint] honey.scanme.sh
--- PASS: TestThreadSafeNuclei (8.79s)
    --- PASS: TestThreadSafeNuclei/scanme.sh (3.62s)
    --- PASS: TestThreadSafeNuclei/honey.scanme.sh (2.83s)
PASS
ok  	github.com/projectdiscovery/nuclei/v3/lib/tests	20.798s

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)