add ability to create manual labels (#18303)

relates to #17031

Adds functionality to create manual labels in fleet.

- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [x] Added/updated tests
- [x] M0anual QA for all new/changed functionality

---------

Co-authored-by: Martin Angers <martin.n.angers@gmail.com>

changes/17899-add-manual-labels-api

@@ -0,0 +1 @@
+* Updated the `POST /api/v1/fleet/labels` and `PATCH /api/v1/fleet/labels/{id}` endpoints to support creation and update of manual labels.

changes/issue-17898-new-manual-lables

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+- implement manual labels in fleet UI