Move template circuits to dedicated page

[Gyan-max]

Summary

Move template circuits to a dedicated documentation page (#14116)

Details and comments

This PR addresses issue #14116 by moving the template circuits documentation from the main circuit library page to a dedicated page. Template circuit are not part of the typical circuit library components and serve a specific purpose in circuit optimization.

Changes:

• Created docs/apidoc/template_circuits.rst containing all template circuit documentation
• Removed detailed template circuit content from qiskit/circuit/library/__init__.py and added a reference to the new page
• Added the template circuits page to the documentation index

No test needed, as this is a documentation-only change that does not affect any functionality.

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