[doc] Completely replace docgen with hugo

This change completely replaces docgen and replaces or removes
docgen-specific markdown in documentation.  It also does the following:

  * Updates all local links to use hugo relative references so that a
    broken link is a broken build.
  * Uses upstream wavedrom, which breaks at least one page that depends
    on local modifications.
  * Renames most hw/ip/**/ip_name.doc and dv_plan documents for a more
    aesthetic document tree layout.
  * Moves some doc/ pages into their own page bundle.
  * Updates util/build_docs.py to pre-generate registers, hwcfg, and
    dashboard fragments and invoke hugo.
diff --git a/doc/rm/python_coding_style.md b/doc/rm/python_coding_style.md
index 244c9f5..3f4dcc5 100644
--- a/doc/rm/python_coding_style.md
+++ b/doc/rm/python_coding_style.md
@@ -1,4 +1,6 @@
-{{% lowrisc-doc-hdr Python Coding Style Guide }}
+---
+title: "Python Coding Style Guide"
+---
 
 ## Basics
 
@@ -17,7 +19,6 @@
 *   promote best practices
 *   increase code sharing and re-use
 
-{{% toc 3 }}
 
 ### Terminology Conventions