Deprecate tracing package

[AbhiPrasad]

Let's mark the import as deprecated with the new instructions. Dependent on getsentry/sentry-docs#6518 getting completed first.

[timfish]

I'm not sure if it's possible to display a deprecation warning for a bare import:

import '@sentry/tracing';

We could log a warning but that would be quite intrusive. We can deprecate all the exports which should cover most usages.

[AbhiPrasad]

We can deprecate all the exports which should cover most usages.

I think this should be good enough! We also then need to update the README of the package with new guidance.