fix: Restrict subscriptions WS server to add listeners only to its own path

[GValeriy]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A
We have a shared Nest server, which serves both Next.js and nestjs/graphQL.
GraphQL WS server conflicts and aborts requests to Next.js, sending to path - "/_next/webpack-hmr".

Next version is 12.2.3.

Nextjs WS server looks like has such path check on its side -
https://github.com/vercel/next.js/blob/0f99768f9811fdf027a083471bd2a435f6207f4a/packages/next/server/dev/next-dev-server.ts#L638-L645

What is the new behavior?

The "nestjs/graphql" package will upgrade listeners only for its path and won't conflict.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[kamilmysliwiec]

LGTM