[otelcol docs] Create new "Extend the Collector" section and rename child pages

[tiffany76]

What needs to be changed?

We are creating a new "extend" section in the Collector docs. This section will contain the OCB and custom component pages, which need to be renamed. Finally, a "build from source" page should be created, but hidden.

What is the name + path of the page that needs changed?

New paths will be created.

These are the pages that need to be moved/renamed:
https://opentelemetry.io/docs/collector/custom-collector/
https://opentelemetry.io/docs/collector/building/ + child pages

Additional context:

There are several tasks needed to complete this issue:

• Create a new top-level page: docs/collector/extend/ called "Extend the Collector"
  • Add a brief introduction to this landing page
• Create new hidden child page: docs/collector/extend/build-from-source
  • Add front matter for this new page, including the following fields:

  build:
    list: never
  draft: true
  toc_hide: true
  

• Create new landing page: docs/collector/extend/custom-component/extension/
  • Add a brief introduction to this landing page
• Rename pages:
  • docs/collector/custom-collector/ to docs/collector/extend/ocb/
  • docs/collector/building/ to docs/collector/extend/custom-component/
  • docs/collector/building/receiver/ to docs/collector/extend/custom-component/receiver/
  • docs/collector/building/connector/ to docs/collector/extend/custom-component/connector/
  • docs/collector/building/authenticator-extension to docs/collector/extend/custom-component/extension/authenticator/
• Add an alias to the front matter of each renamed page pointing to the old page path
• Correct any cross-references to the old page paths, including hashes
  • /docs/collector/custom-collector/, plus page heading anchors
    • platforms/kubernetes/operator/_index.md: line 87
    • security/config-best-practies.md: line 44
    • collector/distributions.md: line 23
    • collector/quick-start.md: line 139
    • collector/building/connector/index.md: line 463
    • collector/building/connector/index.md: line 469
    • collector/building/connector/index.md: line 748
    • collector/building/receiver.md: line 53
    • collector/building/receiver.md: line 56
  • /docs/collector/building/, plus three child pages and page heading anchors
    • collector/distributions.md:20
    • collector/distributions.md:21
    • collector/distributions.md:22
    • collector/custom-collector.md:364
    • collector/custom-collector.md:365
    • collector/configuration.md:738
  • Run a search across the en docs for any other instances of the old page paths and fix them

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