Merge PR: iavl optimzie when delta disable (#1724)
* calcHeightAndSize opt
* if delta off, don't use map of saveNodes
* usafe string to slice
* test GetNode
* Revert "test GetNode"
This reverts commit ae5ee27bcfca7e130bb357f83a34cc2beb9bffc5.
* if produceDelta is false, we don't need to update tree.deltas
* don't need to generate empty slice
* Revert "don't need to generate empty slice"
This reverts commit 73cd0df5a5597c11141328f13a6d878e04e1af91.
Co-authored-by: chengzhinei <chengxue5yuan@163.com>
Co-authored-by: xiangjianmeng <805442788@qq.com>