We have added a new function, SystemCatalog::upgrade(), which will
create a new column in the database and fill it with default values.
It uses a reference column to fill the column, which is passed as a
std::unordered_map<key, value> value to SystemCatalog::upgrade()
function, where key is the target column which needs to be created.
In addition, we pass additional std::unordered_map's to
SystemCatalog::upgrade() containing information such as the datatypes
and colwidths of the target and reference columns, as well as the
default value which will be used to fill the target column.
This does the following:
* Switch resource manager to a singleton which reduces the amount of
times the XML data is scanned and objects allocated.
* Make the I_S tables use the FE implementation of the system catalog
* Make the I_S.columnstore_columns table use the RID list cache
* Make the extentmap pre-allocate a vector instead of many small allocs
