fix: Add missing otelcol alias to make OTel Engine work with OTel Collector helm chart

[thampiotr]

Brief description of Pull Request

Turns out that we cannot change the OTel Collector Helm Chart's args to prepend an otel subcommand. To allow using Alloy's OTel Engine with OTel ecosystem more broadly, we add an otelcol alias to Alloy's Docker image.

Pull Request Details

Issue(s) fixed by this Pull Request

Notes to the Reviewer

This should be tested in the future integration test. For now I verified in local cluster:

root@otelcol-opentelemetry-collector-7786f6d646-fcklr:/# cat /bin/otelcol
#!/usr/bin/env sh
# Compatibility wrapper for OpenTelemetry Collector integrations.
# Delegate to Alloy's OTel engine and pass through all arguments.
exec /bin/alloy otel "$@"

PR Checklist

• Documentation added
• Tests updated
• Config converters updated

[Copilot]

Pull request overview

Adds an otelcol compatibility alias to Alloy’s container images so OpenTelemetry ecosystem tooling (notably the OTel Collector Helm chart) can invoke Alloy’s OTel engine without needing to prepend an otel subcommand.

Changes:

• Add a Linux /bin/otelcol wrapper script that delegates to alloy otel.
• Add a Windows otelcol.cmd wrapper that delegates to alloy.exe otel.
• Update Linux and Windows Dockerfiles to include these compatibility wrappers in the final images.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packaging/docker/otelcol.sh	Adds a small shell wrapper that maps otelcol ... → alloy otel ....
packaging/docker/otelcol.cmd	Adds a Windows CMD wrapper that maps otelcol ... → alloy.exe otel ....
Dockerfile	Installs /bin/otelcol into the Linux image and ensures it is executable.
Dockerfile.windows	Installs otelcol.cmd into the Windows image for compatibility use cases.

[blewis12]

LGTM trying it out locally - perhaps we can add a follow up issue for integration testing