Properly attribute vendored code

[AbhiPrasad]

ref: getsentry/open-source-pledge#120

All of our vendored code has links - but we need to add their license text to top of file as well.

### Tasks
- [ ] https://github.com/getsentry/sentry-javascript/pull/7629
- [ ] https://github.com/getsentry/sentry-javascript/pull/7633
- [ ] #7620
- [x] Next.js
- [x] Web Vitals
- [x] Angular
- [ ] https://github.com/getsentry/sentry-javascript/pull/7635

[timfish]

I think we might be missing links/comments for tracekit and node-stacktrace.

I thought maybe they'd been lost in a refactor but looked back and they never had comments.

I don't mind looking back through the history and adding this.

[AbhiPrasad]

@timfish let's do it!

Process is

1. Vendored code should be in it's own file when possible
2. Code should have a direct permalink to source
3. Code should have license above it

[AbhiPrasad]

I looked at Next.js and Angular and it seems we don't vendor code, we just reference implementation to guide our own code.

Web Vitals also has the license attached to the code everywhere.