Remove all unnecessary includes

All includes from .cc to .h are preserved, even when transitively included.

It's clear that there are far too many includes in header files, and we should be more aggressive with forward declarations. tint:532 will continue to track this work.

There are, however, plenty of includes that have accumulated over time which are no longer required directly or transitively, so this change starts with a clean slate of *required* includes.

Bug: tint:532
Change-Id: Ie1718dad565f8309fa180ef91bcf3920e76dba18
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/44042
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>

src/utils/command_posix.cc

@@ -14,16 +14,10 @@
 
 #include "src/utils/command.h"
 
-#include <errno.h>
-#include <stdio.h>
-#include <stdlib.h>
 #include <sys/poll.h>
 #include <sys/stat.h>
-#include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
-#include <cassert>
-#include <cstring>
 #include <sstream>
 #include <vector>
 

src/utils/tmpfile_posix.cc

@@ -14,9 +14,7 @@
 
 #include "src/utils/tmpfile.h"
 
-#include <stdio.h>
 #include <unistd.h>
-#include <cstdio>
 
 namespace tint {
 namespace utils {

src/utils/unique_vector.h

@@ -47,7 +47,7 @@ struct UniqueVector {
   ConstIterator end() const { return vector.end(); }
 
   /// @returns a const reference to the internal vector
-  operator const std::vector<T> &() const { return vector; }
+  operator const std::vector<T>&() const { return vector; }
 
  private:
   std::vector<T> vector;