feat(node)!: Make dataloader and knex integrations channel-only - #22754

Add `dataloaderIntegration` and `knexIntegration` to `getTracingIntegrations()`
so both are registered by default like every other channel-based integration.

`dataloader` was removed from the defaults in v8 (#13873) due to an upstream
OpenTelemetry bug (#13869) that broke custom DataLoader subclass methods. That
issue is now closed and fixed upstream, and since #22754 the integration is
channel-only — it no longer wraps/replaces the DataLoader class, so the original
breakage mechanism no longer applies. `knex` was never enabled by default.

Drop the now-redundant explicit registration from the node integration-test
instrument files so they exercise the default path.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

Adds `dataloaderIntegration` and `knexIntegration` to
`getTracingIntegrations()`, so both ship as default tracing integrations
like every other channel-based integration, rather than requiring users
to register them manually.

Both were the only two orchestrion-instrumented integrations that are
publicly exported and have channel definitions but were absent from the
default set. Investigating why surfaced that neither omission is still
justified:

- **`dataloader`** was originally a default (added in #13664) but was
removed in #13873 because of an upstream OpenTelemetry bug (#13869)
where instrumenting DataLoader broke custom subclass methods
(`context.dataloaders.x.loadByInternalId is not a function`). That issue
was fixed upstream
([open-telemetry/opentelemetry-js-contrib#2498](open-telemetry/opentelemetry-js-contrib#2498))
and closed on 2025-08-11, confirmed resolved on v10. On top of that,
since #22754 the integration is channel-only: it instruments via
`diagnostics_channel` and no longer wraps/replaces the `DataLoader`
class, so the mechanism that caused the original breakage no longer
exists. There is no remaining reason to keep it opt-in.
- **`knex`** was never enabled by default — it was introduced (#13526)
purely as an opt-in integration with no accompanying default-list
change. There's no documented reason for it to stay opt-in, and it uses
the same channel mechanism as the other DB integrations that are on by
default.

Users can still disable either via `defaultIntegrations`.

The now-redundant explicit `dataloaderIntegration()` /
`knexIntegration()` registrations are dropped from the node
integration-test instrument files so those suites now exercise the
default-registration path. The dataloader suite passes with no explicit
registration, confirming the default wiring works end-to-end.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.8 (1M context) <[email protected]>