Check escape sequence bytes before counting them (#4929)

The parser decided how many bytes a key used before checking them, so a
key that arrived in the same read was lost or misread.

- Recognize F1-F8 and modified Delete, PageUp and PageDown when more input
  follows them, as with a paste or tmux send-keys. They required the
  sequence to be the whole buffer.
- After \e[ and a digit, do not consume a byte that cannot continue the
  sequence. ALT-[, 2 and Enter lost the Enter.
- Report Home and End for \e[7, \e[4 and \e[8 only before ~, $, ^ or @.
  ALT-[, 4 and x fired End and lost the x.
- Look for the end of a mouse report within its frame. A later M swallowed
  the keys before it, and repeated \e[< took quadratic time.

CHANGELOG.md

@@ -5,6 +5,7 @@ CHANGELOG
 ------
 - Fixed `--gap-line` cutting a grapheme cluster when filling the last cells of the line (#4920)
 - Fixed an escape sequence fzf does not recognize being partly consumed, which leaked the rest into the query (#4926)
+- Fixed a key lost when it arrived in the same read as an escape sequence
 
 0.74.4
 ------