Use gitrepo.GetTreePathLatestCommit to get file lastest commit instead from latest commit cache (#32987)

The latest commit cache is currently used only for listing tree files.
However, a cold start may take longer than directly invoking the Git
command. This PR addresses the issue of slow response times when
accessing raw files, improving performance in such scenarios.

```log
gitea.log:105521:2024/12/23 08:22:18 ...eb/routing/logger.go:68:func1() [W] router: slow      GET /xxxx/xxxxxx/raw/commit/xxxxxxxxxxxxxxxxxxxxxxxxxxx/.editorconfig for 172.18.0.5:53252, elapsed 3526.8ms @ repo/download.go:117(repo.SingleDownload)
```

routers/api/v1/repo/file.go

@@ -11,7 +11,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"path"
 	"strings"
 	"time"
 
@@ -242,19 +241,14 @@ func getBlobForEntry(ctx *context.APIContext) (blob *git.Blob, entry *git.TreeEn
 		return nil, nil, nil
 	}
 
-	info, _, err := git.Entries([]*git.TreeEntry{entry}).GetCommitsInfo(ctx, ctx.Repo.Commit, path.Dir("/" + ctx.Repo.TreePath)[1:])
+	latestCommit, err := ctx.Repo.GitRepo.GetTreePathLatestCommit(ctx.Repo.Commit.ID.String(), ctx.Repo.TreePath)
 	if err != nil {
-		ctx.Error(http.StatusInternalServerError, "GetCommitsInfo", err)
+		ctx.Error(http.StatusInternalServerError, "GetTreePathLatestCommit", err)
 		return nil, nil, nil
 	}
+	when := &latestCommit.Committer.When
 
-	if len(info) == 1 {
-		// Not Modified
-		lastModified = &info[0].Commit.Committer.When
-	}
-	blob = entry.Blob()
-
-	return blob, entry, lastModified
+	return entry.Blob(), entry, when
 }
 
 // GetArchive get archive of a repository