Allow configuring hostNetwork for integrations

[iarlyy]

PR Description

This PR implements the ability of setting hostNetwork pod attribute for integration pods. This may be required for example by node_exporter pods, that need to access /proc/sys/net for gathering host level network metrics.

Which issue(s) this PR fixes

Fixes https://github.com/grafana/alloy/issues/250

Notes to the Reviewer

PR Checklist

• [ ] CHANGELOG.md updated
• [x] Documentation added
• [x] Tests updated

[CLAassistant]

All committers have signed the CLA.

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