refactor: rename "process" => "proc" #30387

Problem:
- "process" is often used as a verb (`multiqueue_process_events`), which
  is ambiguous for cases where it's used as a topic.
- The documented naming convention for processes is "proc".
  - `:help dev-name-common`
- Shorter is better, when it doesn't harm readability or
  discoverability.

Solution:
Rename "process" => "proc" in all C symbols and module names.

src/clint.py

@@ -848,7 +848,7 @@ def CheckIncludes(filename, lines, error):
             or filename.endswith('.in.h')
             or FileInfo(filename).RelativePath() in {
         'func_attr.h',
-        'os/pty_process.h',
+        'os/pty_proc.h',
     }):
         return
 
@@ -869,7 +869,7 @@ def CheckIncludes(filename, lines, error):
             "src/nvim/msgpack_rpc/unpacker.h",
             "src/nvim/option.h",
             "src/nvim/os/pty_conpty_win.h",
-            "src/nvim/os/pty_process_win.h",
+            "src/nvim/os/pty_proc_win.h",
                              ]
 
     skip_headers = [