Expand and escape environment variables correctly in outtmpl

Fixes: https://www.reddit.com/r/youtubedl/comments/otfmq3/ytdlp_same_parameters_different_results

yt_dlp/utils.py

@@ -4438,8 +4438,8 @@ OUTTMPL_TYPES = {
 # As of [1] format syntax is:
 #  %[mapping_key][conversion_flags][minimum_width][.precision][length_modifier]type
 # 1. https://docs.python.org/2/library/stdtypes.html#string-formatting
-STR_FORMAT_RE = r'''(?x)
-    (?<!%)
+STR_FORMAT_RE_TMPL = r'''(?x)
+    (?<!%)(?P<prefix>(?:%%)*)
     %
     (?P<has_key>\((?P<key>{0})\))?  # mapping key
     (?P<format>
@@ -4447,10 +4447,11 @@ STR_FORMAT_RE = r'''(?x)
         (?:\d+)?  # minimum field width (optional)
         (?:\.\d+)?  # precision (optional)
         [hlL]?  # length modifier (optional)
-        [diouxXeEfFgGcrs]  # conversion type
+        {1}  # conversion type
     )
 '''
 
+STR_FORMAT_TYPES = 'diouxXeEfFgGcrs'
 
 def limit_length(s, length):
     """ Add ellipses to overly long strings """