This commit adds associated type to "NodeEnv" trait, called "Fs".
The "Fs" type has a trait bound on "NodeFs", which specifies APIs
required for all ops and resolution APIs to function.
A "RealFs" implementation of "NodeFs" is exported from the "deno_node"
crate, that provides a default implementation for the trait.
All code in "deno_node" extension was changed to use the "NodeFs" trait
to handle file system operations, instead of relying on APIs from the
standard library.
This commit changes the type parameter for "deno_node" extension, from
`P: NodePermission` to `Env: NodeEnv`.
`NodeEnv` is a new trait that has associated type `P: NodePermission`.
This is a stepping stone to support swappable file system for the
extension, that will be added as a second associated type to the
`NodeEnv` trait.
This commit moves some code around from "cli/node/mod.rs" to
"ext/node". Additionally "ext/node" was changed to factor out
"ops.rs" and "polyfill.rs" modules.
