(maint) Add traits for folding tests (#837)

This commit adds trait attributes to the Code Folding tests, to make development
faster by making it possible to run only a subset of tests.

Author: glennsarti

test/PowerShellEditorServices.Test/Language/TokenOperationsTests.cs

@@ -154,6 +154,7 @@ private void AssertFoldingReferenceArrays(
             Assert.Equal(expected.Length, actual.Length);
         }
 
+        [Trait("Category", "Folding")]
         [Fact]
         public void LaguageServiceFindsFoldablRegionsWithLF() {
             // Remove and CR characters
@@ -164,6 +165,7 @@ public void LaguageServiceFindsFoldablRegionsWithLF() {
             AssertFoldingReferenceArrays(expectedAllInOneScriptFolds, result);
         }
 
+        [Trait("Category", "Folding")]
         [Fact]
         public void LaguageServiceFindsFoldablRegionsWithCRLF() {
             // The Foldable regions should be the same regardless of line ending type
@@ -178,6 +180,7 @@ public void LaguageServiceFindsFoldablRegionsWithCRLF() {
             AssertFoldingReferenceArrays(expectedAllInOneScriptFolds, result);
         }
 
+        [Trait("Category", "Folding")]
         [Fact]
         public void LaguageServiceFindsFoldablRegionsWithoutLastLine() {
             FoldingReference[] result = GetRegions(allInOneScript, false);
@@ -191,6 +194,7 @@ public void LaguageServiceFindsFoldablRegionsWithoutLastLine() {
             AssertFoldingReferenceArrays(expectedFolds, result);
         }
 
+        [Trait("Category", "Folding")]
         [Fact]
         public void LaguageServiceFindsFoldablRegionsWithMismatchedRegions() {
             string testString =
@@ -210,6 +214,7 @@ public void LaguageServiceFindsFoldablRegionsWithMismatchedRegions() {
             AssertFoldingReferenceArrays(expectedFolds, result);
         }
 
+        [Trait("Category", "Folding")]
         [Fact]
         public void LaguageServiceFindsFoldablRegionsWithDuplicateRegions() {
             string testString =
@@ -230,6 +235,7 @@ public void LaguageServiceFindsFoldablRegionsWithDuplicateRegions() {
 
         // This tests that token matching { -> }, @{ -> } and
         // ( -> ), @( -> ) and $( -> ) does not confuse the folder
+        [Trait("Category", "Folding")]
         [Fact]
         public void LaguageServiceFindsFoldablRegionsWithSameEndToken() {
             string testString =