[Proposal] Post-Review Update for ProgressManager proposal (#1498)

* add v6 update + rename file to ProgressManager

* add support for UInt64 and Duration types

* remove duplicate summary methods

* remove duplicate subscript methods

* fix example

* update availability

* sync progress manager code documentation

* fix code documentation

* fix typo

* change from struct to enum + fix formatting

* remove ProgressManager prefix for Values and Property

* add typealiases to ProgressReporter

* make enums frozen

* update example to use enum

* update proposal: setCounts + moving dynamicMemberLookup to ProgressManager

Author: chloe-yeo