bluetooth: shell: refactor shell print to eliminate ctx_shell usage

This change aims to eliminate the dependency on `ctx_shell` in
the Bluetooth `host/shell/*`, making the code more maintainable.
Replaced `shell_*` functions that depended on `ctx_shell` with
the appropriate `bt_shell_*` functions.

The shell-less functions `bt_do_scan_off` and `bt_do_connect_le`
were added so they can be called in `cmd_scan_off`, `cmd_connect_le`,
and `scan_recv`.

Signed-off-by: Pisit Sawangvonganan <[email protected]>