global: use '/usr/bin/env bash' instead of '/usr/bin/bash' in shebangs

Using the method from @cemeyer
(https://github.com/espressif/esp-idf/pull/3166):

find . -name \*.sh -exec sed -i "" -e 's|^#!.*bin/bash|#!/usr/bin/env bash|' {} +

Closes https://github.com/espressif/esp-idf/pull/3166.

tools/ci/check-executable.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # This script finds executable files in the repository, excluding some directories,
 # then prints the list of all files which are not in executable-list.txt.
 # Returns with error if this list is non-empty.