fix data race in templates with payloads

[tarunKoyalwar]

Proposed changes

• Newly generated payloads using generator were passed by reference instead of value which caused data race . This is corrected with this PR

• Issue can be reproduced with fatal error: concurrent map writes #3253 (comment)

• closes fatal error: concurrent map writes #3253

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)

[tarunKoyalwar]

Demo

$  GORACE="halt_on_error=1" go run -race . -u scanme.sh -t ~/test/parallel.yaml

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v2.8.8

		projectdiscovery.io

[INF] Using Nuclei Engine 2.8.8 (latest)
[INF] Using Nuclei Templates 9.3.6 (latest)
[INF] Templates added in last update: 30
[INF] Templates loaded for scan: 1
[INF] Targets loaded for scan: 1
[INF] Running httpx on input host
[INF] Found 1 URL from httpx
[INF] No results found. Better luck next time!