[vm, docs] Describe which VM service features are available in which VM modes.
[vm, docs] Describe which VM service features are available in which VM modes.

Change-Id: Icafc5cbea40eb74caf5be26def5641ce3dd855d2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/133427
Reviewed-by: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk