[parser] model: move placement policy definition into 2 parser (#1327)
[parser] model: move placement policy definition into 2 parser (#1327)

 
c4pt0r/tidb,kyle-wang/tidb,kyle-wang/tidb,pingcap/tidb,pingcap/tidb,kyle-wang/tidb,ngaut/tidb,c4pt0r/tidb,c4pt0r/tidb,c4pt0r/tidb,kyle-wang/tidb,ngaut/tidb,pingcap/tidb,coocood/tidb,pingcap/tidb,c4pt0r/tidb,pingcap/tidb,ngaut/tidb,kyle-wang/tidb,ngaut/tidb,coocood/tidb,kyle-wang/tidb,c4pt0r/tidb,ngaut/tidb,ngaut/tidb,pingcap/tidb