* Add merge helper for string maps
* structs: add statuses, MaxClientDisconnect, and helper funcs
* taintedNodes: Include disconnected nodes
* upsertAllocsImpl: don't use existing ClientStatus when upserting unknown
* allocSet: update filterByTainted and add delayByMaxClientDisconnect
* allocReconciler: support disconnecting and reconnecting allocs
* GenericScheduler: upsert unknown and queue reconnecting

Co-authored-by: Tim Gross <tgross@hashicorp.com>

* api: Add struct, conversion function, and tests
* TaskGroup: Add field, validation, and tests
* diff: Add diff handler and test
* docs: Update docs

* structs: Add alloc.Expired & alloc.Reconnected functions. Add Reconnect eval trigger by.

* node_endpoint: Emit new eval for reconnecting unknown allocs.

* filterByTainted: handle 2 phase commit filtering rules.

* reconciler: Append AllocState on disconnect. Logic updates from testing and 2 phase reconnects.

* allocs: Set reconnect timestamp. Destroy if not DesiredStatusRun. Watch for unknown status.

* TaskGroup: Validate that max_client_disconnect and stop_after_client_disconnect are mutually exclusive.

…ined allocs.