gh-100001: Also escape \s in http.server log messages. (GH-100038)

Also \ escape \s in the http.server BaseHTTPRequestHandler.log_message so
that it is technically possible to parse the line and reconstruct what the
original data was.  Without this a \xHH is ambiguious as to if it is a hex
replacement we put in or the characters r"\x" came through in the original
request line.
(cherry picked from commit 7e29398407)

Co-authored-by: Gregory P. Smith <greg@krypto.org>

Lib/http/server.py

@@ -566,6 +566,7 @@ class BaseHTTPRequestHandler(socketserver.StreamRequestHandler):
     # https://en.wikipedia.org/wiki/List_of_Unicode_characters#Control_codes
     _control_char_table = str.maketrans(
             {c: fr'\x{c:02x}' for c in itertools.chain(range(0x20), range(0x7f,0xa0))})
+    _control_char_table[ord('\\')] = r'\\'
 
     def log_message(self, format, *args):
         """Log an arbitrary message.