Fix Version/s: None
DM-22698, DM-23094, and DM-22461 we incorporated Doxygen builds for Pipelines docs directly into Documenteer, migrating away from our dependency on sconsUtils and lsstDoxygen. This included consolidating the Doxygen configuration, while still allowing individual packages a limited vocabulary of Doxygen configuration tags to include or exclude specific paths from the documentation.
We've discovered, though, that the base package actually plays a special role in providing configuration defaults beyond those coded into sconsUtils.
Thus in this ticket we will port base's configurations into documenteer and expand documenteer's Doxygen configuration facility to handle these new tags.
1. Port the `base.inc`, `pex_config.inc` and `pex_exceptions.inc` files from their respective packages into a Doxygen default configuration that's included with Documenteer and included in the Doxygen config via `@INCLUDE_PATH` and `@INCLUDE` Doxygen configuration tags.
2. Embed the Doxygen tag file for cppreference.com, which was previously stored in the base package as well.
3. Add `IMAGE_PATH` Doxygen configuration and make it something that can be set from individual packages.
4. Include `src/` directories and `.cc` files in Doxygen inputs as that matches existing usage.
5. Add Doxygen logging configurations to DoxygenConfiguration to enable future dynamic settings.
The net effect is that the Doxygen builds controlled by Documenteer now match the functionality of `sconsUtils`, `lsstDoxygen`, etc. in terms of fully reproducing the `lsst` namespace.