managen: introduce "Multi: per-URL"

For -O, -o and -T that are used once per specified URL.

Closes #14045

docs/cmdline-opts/MANPAGE.md

@@ -45,7 +45,7 @@ A line that starts with `<!--` is a comment. It should also end with `-->`.
     Help: (short text for the --help output for this option)
     Long: (long form name, without dashes)
     Magic: (description of "magic" options)
-    Multi: single/append/boolean/mutex/custom (if used more than once)
+    Multi: single/append/boolean/mutex/custom/per-URL (if used more than once)
     Mutexed: (space separated list of options this overrides, no dashes)
     Protocols: (space separated list for which protocols this option works)
     Requires: (space separated list of features this requires, no dashes)

docs/cmdline-opts/output.md

@@ -7,7 +7,7 @@ Short: o
 Help: Write to file instead of stdout
 Category: important curl
 Added: 4.0
-Multi: append
+Multi: per-URL
 See-also:
   - remote-name
   - remote-name-all

docs/cmdline-opts/remote-name.md

@@ -6,13 +6,14 @@ Short: O
 Help: Write output to file named as remote file
 Category: important output
 Added: 4.0
-Multi: append
+Multi: per-URL
 See-also:
   - remote-name-all
   - output-dir
   - remote-header-name
 Example:
   - -O https://example.com/filename
+  - -O https://example.com/filename -O https://example.com/file2
 ---
 
 # `--remote-name`

docs/cmdline-opts/upload-file.md

@@ -7,7 +7,7 @@ Arg: <file>
 Help: Transfer local FILE to destination
 Category: important upload
 Added: 4.0
-Multi: append
+Multi: per-URL
 See-also:
   - get
   - head
@@ -17,6 +17,7 @@ Example:
   - -T file $URL
   - -T "img[1-1000].png" ftp://ftp.example.com/
   - --upload-file "{file1,file2}" $URL
+  - -T file -T file2 $URL $URL
 ---
 
 # `--upload-file`