1.Support setting up the line height and additional kerning of label.
2.Add more annotation
add assert.
Merge pull request #7118 from natural-law/v3

Remove the debug symbols for release mode in xcode projects.
add test case for new API of Label.
Merge pull request #7046 from Dhilan007/v3-label-improve

1.Support setting up the line height and additional kerning of label.