* [sonic-cfggen] optimize execution time
a lot of template rendering causes switch to start longer because jinja2
needs to parse them. Introducing RedisBytecodeCache to store parsed buckets of
internal template bytecode to speedup same template rendering during start
* [sonic-cfggen] do lazy regexp compilation to speedup sonic-cfggen
* [sonic-cfggen] address pep8 related comments
Signed-off-by: Stepan Blyschak <stepanb@mellanox.com>
