Convert test_cgi to unittest.

Lib/test/output/test_cgi

-test_cgi
-'' => []
-'&' => []
-'&&' => []
-'=' => [('', '')]
-'=a' => [('', 'a')]
-'a' => [('a', '')]
-'a=' => [('a', '')]
-'a=' => [('a', '')]
-'&a=b' => [('a', 'b')]
-'a=a+b&b=b+c' => [('a', 'a b'), ('b', 'b c')]
-'a=1&a=2' => [('a', '1'), ('a', '2')]
-''
-'&'
-'&&'
-';'
-';&;'
-'='
-'=&='
-'=;='
-'=a'
-'&=a'
-'=a&'
-'=&a'
-'b=a'
-'b+=a'
-'a=b=a'
-'a=+b=a'
-'&b=a'
-'b&=a'
-'a=a+b&b=b+c'
-'a=a+b&a=b+a'
-'x=1&y=2.0&z=2-3.%2b0'
-'x=1;y=2.0&z=2-3.%2b0'
-'x=1;y=2.0;z=2-3.%2b0'
-'Hbc5161168c542333633315dee1182227:key_store_seqid=400006&cuyer=r&view=bustomer&order_id=0bb2e248638833d48cb7fed300000f1b&expire=964546263&lobale=en-US&kid=130003.300038&ss=env'
-'group_id=5470&set=custom&_assigned_to=31392&_status=1&_category=100&SUBMIT=Browse'
-Testing log
-Testing initlog 1
-Testing log 2
-Test FieldStorage methods that use readline
-Test basic FieldStorage multipart parsing