chore(Combinatorics/SimpleGraph/Coloring): move Coloring.lean to Coloring/VertexColoring.lean (#37525)

This is in preparation of #33313 and other material to come, here's how I imagine the folder to look like:
- `Coloring/VertexColoring.lean` (currently `Coloring.lean`)
- `Coloring/EdgeColoring.lean`
- `Coloring/VertexListColoring.lean`
- `Coloring/EdgeListColoring.lean`
- `Coloring/ChromaticPolynomial.lean`
- `Coloring/EdgeLabeling.lean` (currently `./EdgeLabeling.lean`)
- `Coloring/ConcreteColorings.lean` (currently `./ConcreteColorings.lean`)

Author: SnirBroshi

Mathlib.lean

@@ -3483,7 +3483,7 @@ public import Mathlib.Combinatorics.SimpleGraph.Basic
 public import Mathlib.Combinatorics.SimpleGraph.Bipartite
 public import Mathlib.Combinatorics.SimpleGraph.Circulant
 public import Mathlib.Combinatorics.SimpleGraph.Clique
-public import Mathlib.Combinatorics.SimpleGraph.Coloring
+public import Mathlib.Combinatorics.SimpleGraph.Coloring.VertexColoring
 public import Mathlib.Combinatorics.SimpleGraph.CompleteMultipartite
 public import Mathlib.Combinatorics.SimpleGraph.ConcreteColorings
 public import Mathlib.Combinatorics.SimpleGraph.Connectivity.Connected

Mathlib/Combinatorics/SimpleGraph/Bipartite.lean

@@ -7,7 +7,7 @@ module
 
 public import Mathlib.Algebra.Notation.Indicator
 public import Mathlib.Combinatorics.Enumerative.DoubleCounting
-public import Mathlib.Combinatorics.SimpleGraph.Coloring
+public import Mathlib.Combinatorics.SimpleGraph.Coloring.VertexColoring
 public import Mathlib.Combinatorics.SimpleGraph.Copy
 public import Mathlib.Combinatorics.SimpleGraph.DegreeSum
 

…/Combinatorics/SimpleGraph/Coloring.lean …SimpleGraph/Coloring/VertexColoring.leanMathlib/Combinatorics/SimpleGraph/Coloring.lean renamed to Mathlib/Combinatorics/SimpleGraph/Coloring/VertexColoring.lean Mathlib/Combinatorics/SimpleGraph/Coloring.lean renamed to Mathlib/Combinatorics/SimpleGraph/Coloring/VertexColoring.lean

@@ -5,7 +5,7 @@ Authors: John Talbot, Lian Bremner Tattersall
 -/
 module
 
-public import Mathlib.Combinatorics.SimpleGraph.Coloring
+public import Mathlib.Combinatorics.SimpleGraph.Coloring.VertexColoring
 public import Mathlib.Combinatorics.SimpleGraph.Copy
 public import Mathlib.Combinatorics.SimpleGraph.DegreeSum
 public import Mathlib.Combinatorics.SimpleGraph.Extremal.Turan

Mathlib/Combinatorics/SimpleGraph/CompleteMultipartite.lean

@@ -7,7 +7,7 @@ module
 
 public import Mathlib.Combinatorics.SimpleGraph.Bipartite
 public import Mathlib.Combinatorics.SimpleGraph.Circulant
-public import Mathlib.Combinatorics.SimpleGraph.Coloring
+public import Mathlib.Combinatorics.SimpleGraph.Coloring.VertexColoring
 public import Mathlib.Combinatorics.SimpleGraph.CompleteMultipartite
 public import Mathlib.Combinatorics.SimpleGraph.Hasse
 public import Mathlib.Data.Fin.Parity

Mathlib/Combinatorics/SimpleGraph/ConcreteColorings.lean

@@ -5,7 +5,7 @@ Authors: Arthur Paulino, Kyle Miller
 -/
 module
 
-public import Mathlib.Combinatorics.SimpleGraph.Coloring
+public import Mathlib.Combinatorics.SimpleGraph.Coloring.VertexColoring
 
 /-!
 # Graph partitions

Mathlib/Combinatorics/SimpleGraph/Partition.lean

@@ -6,7 +6,7 @@ Authors: Iván Renison
 module
 
 public import Mathlib.Combinatorics.SimpleGraph.Basic
-public import Mathlib.Combinatorics.SimpleGraph.Coloring
+public import Mathlib.Combinatorics.SimpleGraph.Coloring.VertexColoring
 public import Mathlib.Combinatorics.SimpleGraph.Maps
 
 /-!