MM-29981 - optimize markdown.Inspect (#16188)

* MM-29981 - optimize markdown.Inspect

- Cache regexp.MustCompile
- Reuse slice in MergeInlineText
- Remove pointer to slice in closeBlocks
- Pre-allocate slice in ParseLines
- Some more small cleanups

```
name       old time/op    new time/op    delta
Inspect-8    10.5µs ± 3%     6.6µs ± 1%  -37.59%  (p=0.000 n=10+7)

name       old alloc/op   new alloc/op   delta
Inspect-8    6.66kB ± 0%    3.22kB ± 0%  -51.62%  (p=0.000 n=10+9)

name       old allocs/op  new allocs/op  delta
Inspect-8       117 ± 0%        76 ± 0%  -35.04%  (p=0.000 n=10+10)
```

* fix lint

* remove ignore

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

utils/markdown/blocks.go

@@ -37,13 +37,14 @@ type Range struct {
 	End      int
 }
 
-func closeBlocks(blocks []Block, referenceDefinitions *[]*ReferenceDefinition) {
+func closeBlocks(blocks []Block, referenceDefinitions []*ReferenceDefinition) []*ReferenceDefinition {
 	for _, block := range blocks {
 		block.Close()
 		if p, ok := block.(*Paragraph); ok && len(p.ReferenceDefinitions) > 0 {
-			*referenceDefinitions = append(*referenceDefinitions, p.ReferenceDefinitions...)
+			referenceDefinitions = append(referenceDefinitions, p.ReferenceDefinitions...)
 		}
 	}
+	return referenceDefinitions
 }
 
 func ParseBlocks(markdown string, lines []Line) (*Document, []*ReferenceDefinition) {
@@ -78,7 +79,7 @@ func ParseBlocks(markdown string, lines []Line) (*Document, []*ReferenceDefiniti
 				for i := lastMatchIndex; i >= 0; i-- {
 					if container, ok := openBlocks[i].(ContainerBlock); ok {
 						if addedBlocks := container.AddChild(newBlocks); addedBlocks != nil {
-							closeBlocks(openBlocks[i+1:], &referenceDefinitions)
+							referenceDefinitions = closeBlocks(openBlocks[i+1:], referenceDefinitions)
 							openBlocks = openBlocks[:i+1]
 							openBlocks = append(openBlocks, addedBlocks...)
 							didAdd = true
@@ -98,7 +99,7 @@ func ParseBlocks(markdown string, lines []Line) (*Document, []*ReferenceDefiniti
 			continue
 		}
 
-		closeBlocks(openBlocks[lastMatchIndex+1:], &referenceDefinitions)
+		referenceDefinitions = closeBlocks(openBlocks[lastMatchIndex+1:], referenceDefinitions)
 		openBlocks = openBlocks[:lastMatchIndex+1]
 
 		if openBlocks[lastMatchIndex].AddLine(indentation, r) {
@@ -109,7 +110,7 @@ func ParseBlocks(markdown string, lines []Line) (*Document, []*ReferenceDefiniti
 			for i := lastMatchIndex; i >= 0; i-- {
 				if container, ok := openBlocks[i].(ContainerBlock); ok {
 					if newBlocks := container.AddChild([]Block{paragraph}); newBlocks != nil {
-						closeBlocks(openBlocks[i+1:], &referenceDefinitions)
+						referenceDefinitions = closeBlocks(openBlocks[i+1:], referenceDefinitions)
 						openBlocks = openBlocks[:i+1]
 						openBlocks = append(openBlocks, newBlocks...)
 						break
@@ -119,7 +120,7 @@ func ParseBlocks(markdown string, lines []Line) (*Document, []*ReferenceDefiniti
 		}
 	}
 
-	closeBlocks(openBlocks, &referenceDefinitions)
+	referenceDefinitions = closeBlocks(openBlocks, referenceDefinitions)
 
 	return document, referenceDefinitions
 }