Allow multiple top output wires to come from layers

[adamgerhant]

Closes #1886

Allows vector layers to be joined into a single layer if they are connected by the pen tool

[github-actions]

Found Clippy warnings

Clippy Warnings/Errors

warning: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
   --> node-graph/gcore/src/raster/adjustments.rs:813:3
    |
813 | /         match self {
814 | |             Some(ref mut v) => *v = map_fn(v),
815 | |             None => (),
816 | |         }
    | |_________^ help: try: `if let Some(ref mut v) = self { *v = map_fn(v) }`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#single_match
    = note: `-W clippy::single-match` implied by `-W clippy::all`
    = help: to override `-W clippy::all` add `#[allow(clippy::single_match)]`

warning: `graphene-core` (lib) generated 1 warning (run `cargo clippy --fix --lib -p graphene-core` to apply 1 suggestion)
warning: large size difference between variants
   --> node-graph/graph-craft/src/document/value.rs:28:3
    |
28  | /         pub enum TaggedValue {
29  | |             None,
30  | |             $( $(#[$meta] ) *$identifier( $ty ), )*
    | |                              ------------------ the largest variant contains at least 648 bytes
31  | |             RenderOutput(RenderOutput),
    | |             -------------------------- the second-largest variant contains at least 216 bytes
...   |
34  | |             EditorApi(Arc<WasmEditorApi>)
35  | |         }
    | |_________^ the entire enum is at least 0 bytes
...
116 | / tagged_value! {
117 | |     String(String),
118 | |     U32(u32),
119 | |     U64(u64),
...   |
181 | |     FontCache(Arc<graphene_core::text::FontCache>),
182 | | }
    | |_- in this macro invocation
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#large_enum_variant
    = note: `-W clippy::large-enum-variant` implied by `-W clippy::all`
    = help: to override `-W clippy::all` add `#[allow(clippy::large_enum_variant)]`
    = note: this warning originates in the macro `tagged_value` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider boxing the large fields to reduce the total size of the enum
    |
138 |     VectorData(Box<graphene_core::vector::VectorData>),
    |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

warning: `graph-craft` (lib) generated 1 warning
warning: `graphene-core` (lib) generated 1 warning (1 duplicate)
warning: `graph-craft` (lib) generated 1 warning (1 duplicate)
warning: `graph-craft` (lib test) generated 1 warning (1 duplicate)
warning: use of deprecated type alias `std::panic::PanicInfo`: use `PanicHookInfo` instead
  --> website/other/bezier-rs-demos/wasm/src/lib.rs:22:36
   |
22 |         fn panic_hook(info: &std::panic::PanicInfo<'_>) {
   |                                          ^^^^^^^^^
   |
   = note: `#[warn(deprecated)]` on by default

warning: `bezier-rs-wasm` (lib) generated 1 warning
warning: `bezier-rs-wasm` (lib test) generated 1 warning (1 duplicate)
warning: `graphene-core` (lib test) generated 1 warning (1 duplicate)
    Finished `dev` profile [optimized + debuginfo] target(s) in 4m 58s