### Describe Your Changes
Move OpenTelemetry-related documentation under docs/integrations and
docs/data-ingestion to establish a clear, scalable structure.
As OpenTelemetry support expands, we need a dedicated place to document
protocol details, implementation specifics, and known limitations, such
as:
- Delta temporality not working with downsampling. See
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10014#issuecomment-3697509266.
- Negative histogram buckets being discarded by VictoriaMetrics. See
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/9896.
The new structure separates concerns:
- `docs/integrations/` — protocol overview, implementation details, and
limitations.
- `docs/data-ingestion/` — OpenTelemetry Collector configuration and
ingestion setup.
This aligns OpenTelemetry documentation with the existing structure used
across other integrations and ingestion methods.
New pages and links preserve backward compatiblity
### Checklist
The following checks are **mandatory**:
- [ ] My change adheres to [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/victoriametrics/contributing/#pull-request-checklist).
- [ ] My change adheres to [VictoriaMetrics development
goals](https://docs.victoriametrics.com/victoriametrics/goals/).
The new section is supposed to contain otel related information for all
products, like VT, VM, VL.
It also supposed to be visible for readers right away, without need to
dig for info in each product.
It contains basic information and is supposed to act as a router to more
detailed info in each product.
While there, also updated VM-related otel info.
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Depends on
https://github.com/VictoriaMetrics/victoriametrics-datasource/pull/458
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Signed-off-by: hagen1778 <roman@victoriametrics.com>
