Finish converting existing comments for internal API docs (#8146)

* Finish converting existing comments for internal API docs

99% of this was just reformatting existing comments. Only two exceptions:

- Expanded upon `BuildResult::status` compat note

- Split up file-level `symbol-table.hh` doc comments to get
  per-definition docs

Also fixed a few whitespace goofs, turning leading tabs to spaces and
removing trailing spaces.

Picking up from #8133

* Fix two things from comments

* Use triple-backtick not indent for `dumpPath`

* Convert GNU-style `\`..'` quotes to markdown style in API docs

This will render correctly.

src/libutil/thread-pool.hh

@@ -40,15 +40,15 @@ public:
 
     /**
      * Execute work items until the queue is empty.
-     * 
-	 * \note Note that work items are allowed to add new items to the
-	 * queue; this is handled correctly.
      *
-	 * Queue processing stops prematurely if any work item throws an
-	 * exception. This exception is propagated to the calling thread. If
-	 * multiple work items throw an exception concurrently, only one
-	 * item is propagated; the others are printed on stderr and
-	 * otherwise ignored.
+     * \note Note that work items are allowed to add new items to the
+     * queue; this is handled correctly.
+     *
+     * Queue processing stops prematurely if any work item throws an
+     * exception. This exception is propagated to the calling thread. If
+     * multiple work items throw an exception concurrently, only one
+     * item is propagated; the others are printed on stderr and
+     * otherwise ignored.
      */
     void process();