How envoy instantiates HTTP filter? especially for lua filter.

1. Does each request create an instance per HTTP filter configured in the http_filters?
That is, for each request, the connection manager will create a C++ object of `Envoy::Extensions::HttpFilters::Lua::Filter` class (if it's configured in http_filters).
3. Is the same HTTP filter class allowed to be configured multiple times in http_filters?
For example, this yaml specifies two configuration blocks for the same lua filter class.
https://github.com/envoyproxy/envoy/blob/6e706d90b3c5a2947017c77d5bd209f16115dc8a/examples/lua/envoy.yaml#L38-L51
4. Does each source code of lua filter have its own lua vm instance?
Each code block has its own thread-local lua state, i.e. each worker thread has one lua state.
https://github.com/envoyproxy/envoy/blob/6e706d90b3c5a2947017c77d5bd209f16115dc8a/source/extensions/filters/http/lua/lua_filter.h#L49
One config instance of lua filter has one default code block or code black map.
https://github.com/envoyproxy/envoy/blob/6e706d90b3c5a2947017c77d5bd209f16115dc8a/source/extensions/filters/http/lua/lua_filter.cc#L812-L826
So, for each worker thread, it has `` lua VM states, where `` is the number of source code blocks configured?