feat: added support for context cancellation to engine

[Ice3man543]

Proposed changes

• nuclei now support for context cancellation to engine
• nuclei now use more granular timeouts than a global http timeout to better identify and track errors

Before:

• HTTP Timeout (Default) = 10s

After:

• Http Timeout (Default) = 3 * 10s
• ResponseHeaderTimeout = 5 sec

ResponseHeaderTimeout specifies time to wait before receiving the first response header

• timeout awaiting response headers is now included in max-host-error ( this only happens for very slow hosts or infinite hang )

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]

New updates

• we now use more granular timeouts than a global http timeout to better identify and track errors

Before:

• HTTP Timeout (Default) = 10s

After:

• Http Timeout (Default) = 3 * 10s
• ResponseHeaderTimeout = 5 sec

ResponseHeaderTimeout specifies time to wait before receiving the first response header

• timeout awaiting response headers is now included in max-host-error ( this only happens for very slow hosts or infinite hang )

[tarunKoyalwar]

Follow-up Ticket Idea

• context deadline exceeded is too vague of error considering we have context propogated throughout nuclei and context with timeouts are used at various places.

• i suggest we remove context.WithTimeout and replace it with newly introduced timeout with cause https://pkg.go.dev/context#WithTimeoutCause , that way we show/get actual reason why error happened (from cause) instead of just context deadline exceeded

cc: @Ice3man543