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 special handling was added to `cmd_scan_off` and `cmd_connect_le`
because these commands both used the `sh` context and previously
depended on `ctx_shell`.

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