Derive `Hash` while manually implementing `PartialEq`

[tcharding]

For the Miniscript struct

#[derive(Clone, Hash)]
pub struct Miniscript<Pk: MiniscriptKey, Ctx: ScriptContext> {

Clippy warns us that we are deriving Hash and using a custom implementation of PartialEq, this is likely wrong as explained in the lint docs.

Here is the clippy warning

error: you are deriving `Hash` but have implemented `PartialEq` explicitly
  --> src/miniscript/mod.rs:60:17
   |
60 | #[derive(Clone, Hash)]
   |                 ^^^^
   |
   = note: `#[deny(clippy::derive_hash_xor_eq)]` on by default
note: `PartialEq` implemented here
  --> src/miniscript/mod.rs:93:1
   |
93 | / impl<Pk: MiniscriptKey, Ctx: ScriptContext> PartialEq for Miniscript<Pk, Ctx> {
94 | |     fn eq(&self, other: &Miniscript<Pk, Ctx>) -> bool {
95 | |         self.node.eq(&other.node)
96 | |     }
97 | | }
   | |_^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#derive_hash_xor_eq
   = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)

[apoelstra]

Nice, good catch.

It's probably okay here since (in theory) self.node implies all the other fields but if we're going to make that explicit for PartialEq we should do the same for Hash as well.