fix(otel): Add transaction source logic to otel spans

[AbhiPrasad]

Define transaction source on transactions depending on what semantic attributes are being used. See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-server-semantic-conventions.

Related: open-telemetry/opentelemetry-demo#566

[mydea]

l: Instead of adding these tests, maybe it is better to adjust all the tests starting here:

sentry-javascript/packages/opentelemetry-node/test/spanprocessor.test.ts

Line 408 in af9d0f7

it('updates op/description based on attributes for HTTP_METHOD without HTTP_ROUTE', async () => {

to simply also check the source? There are already tests for the different otel attribute variations, IMHO we could just add an expect(sentrySpan?.transaction?.metadata.source).toBe('XXX'); check to all of them?

[AbhiPrasad]

I did this because source only applies for transactions - so I wanted an explicit scenario where we were checking the transaction (span.transaction when it's a transaction is a self reference) for this test. Gonna keep it like this for now, we can always update later on if need be.

[mydea]

LGTM, imho maybe we can restructure the added tests and instead add the check for source to the existing tests of the different scenarios of attributes, but I also don't have strong feelings about this!