bash: update to 5.3 patch level 20

bash: update to 5.3 patch level 20

- Accommodate macOS dynamic pipe sizing, avoiding hangs.
- Modify the readline redisplay code to use a buffer offset instead of
  the physical prompt length in a multibyte locale to determine whether
  to reprint the prompt from column 0 because the cursor is before the
  last invisible character in the prompt string.
- Fix readline crash with a prompt that exceeds 256 wrapped lines.
  Fix readline redisplay code to print the entire prompt if the first
  few characters are identical but part of a terminal escape sequence
  and the prompt needs to be redrawn.
- Work around systems including bytes between 128 and 255 in the
  isalpha(3) set, which causes bash to potentially include them in
  identifier names.
- If readline handles a SIGWINCH and updates its idea of the screen
  dimensions, it needs to recompute the columns where the prompt wraps
  lines every time, not just when the screen width decreases.

Signed-off-by: Wei-Ting Yang <redacted>