Shared reservation

[modular-magician]

Added shareSetting to enable SharedReservation creation for compute.reservation.
ShareSetting includes two properties:
-shareType: LOCAL and SPECIFIC_PROJECTS
-project_map: a map of projectId and projectConfig.

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Release Note Template for Downstream PRs (will be copied)

compute: Added `shareSettings` in `google_compute_reservation`

Derived from GoogleCloudPlatform/magic-modules#5547