[libc][docs] reorganize documentation (#118836)

This commit does a few things:
* creates libc/docs/headers/ and moves all user API related headers under it.
* updates paths and docgen
* updates the top level index to put these headers under a new "Implementation
  Status" tab.
* rename some of the files to be foo.rst for foo.h (except strings, which is
  currently a mix of string.h and stdlib.h)
* update the heading of some files to be in the form foo.h.

libc/docs/headers/complex.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 =========
 complex.h

libc/docs/headers/ctype.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 =======
 ctype.h

libc/docs/headers/fenv.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 ======
 fenv.h

libc/docs/headers/index.rst

@@ -0,0 +1,18 @@
+Implementation Status
+=====================
+
+.. toctree::
+   :maxdepth: 1
+
+   complex
+   ctype
+   fenv
+   math/index.rst
+   search
+   setjmp
+   signal
+   stdbit
+   stdio
+   strings
+   threads
+   time

libc/docs/headers/math/index.rst

@@ -1,10 +1,10 @@
 .. _math:
 
-==============
-Math Functions
-==============
+======
+math.h
+======
 
-.. include:: ../check.rst
+.. include:: ../../check.rst
 
 .. raw:: html
 

libc/docs/headers/math/stdfix.rst

@@ -2,7 +2,7 @@
 StdFix Functions
 ================
 
-.. include:: ../check.rst
+.. include:: ../../check.rst
 
 Standards and Goals
 -------------------

libc/docs/headers/search.rst

@@ -1,8 +1,8 @@
-=============
-Search Tables
-=============
+========
+search.h
+========
 
-.. include:: check.rst
+.. include:: ../check.rst
 
 ---------------
 Source Location

libc/docs/headers/setjmp.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 ========
 setjmp.h

libc/docs/headers/signal.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 ========
 signal.h

libc/docs/headers/stdbit.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 ========
 stdbit.h

libc/docs/headers/stdio.rst

@@ -1,8 +1,8 @@
-===============
-StdIO Functions
-===============
+=======
+stdio.h
+=======
 
-.. include:: check.rst
+.. include:: ../check.rst
 
 ---------------
 Source location

libc/docs/headers/strings.rst

@@ -2,7 +2,7 @@
 String Functions
 ================
 
-.. include:: check.rst
+.. include:: ../check.rst
 
 ---------------
 Source location

libc/docs/headers/threads.rst

@@ -1,4 +1,4 @@
-.. include:: check.rst
+.. include:: ../check.rst
 
 =========
 threads.h

libc/docs/headers/time.rst

@@ -1,8 +1,8 @@
-=======================
-Date and Time Functions
-=======================
+======
+time.h
+======
 
-.. include:: check.rst
+.. include:: ../check.rst
 
 ---------------
 Source location

libc/docs/index.rst

@@ -64,19 +64,8 @@ stages there is no ABI stability in any form.
    :caption: Status
 
    compiler_support
-   date_and_time
-   math/index.rst
-   strings
-   stdio
-   stdbit
-   fenv
-   libc_search
+   headers/index.rst
    c23
-   ctype
-   complex
-   signal
-   threads
-   setjmp
 
 .. toctree::
    :hidden:

libc/utils/docgen/docgen.py

@@ -161,7 +161,7 @@ def print_macros_rst(header: Header, macros: Dict):
 
 
 def print_impl_status_rst(header: Header, api: Dict):
-    print(".. include:: check.rst\n")
+    print(".. include:: ../check.rst\n")
 
     print("=" * len(header.name))
     print(header.name)