Unify python executables to use `#!/usr/bin/env python` shebang (#2102)

* fixed shebangs in tools (and lib)

* fixed shebangs in examples

* do not mangle shebangs in rpm spec

* renamed style-check.sh to c-style-check.sh

* factored out python linter to a separate file

* added shebang validation to the py-style-check

* added shebangs to all python executables
diff --git a/examples/tracing/tcpv4connect.py b/examples/tracing/tcpv4connect.py
index 8a89469..5b03717 100755
--- a/examples/tracing/tcpv4connect.py
+++ b/examples/tracing/tcpv4connect.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 # tcpv4connect	Trace TCP IPv4 connect()s.
 #		For Linux, uses BCC, eBPF. Embedded C.