[V106-specific] When emitting suspension event for Derived Asset pool, check its status rather than the L1 pool's

[V106-specific]

Intended to close #1470 (closed).

Update: A similar modification also added for the checking of the Available status.
Please check whether I have broken anything.

Further update: A regression test now checks the "pool" event emission timing
(as well as that StatusSince doesn't change without event emission) hasn't changed).

Question:
Is it really desired for the Derived Asset pool to inherit
LPUnits and SynthUnits and PendingInboundRune and PendingInboundAsset from the reference pool,
or would it be acceptable/appropriate for these to be 0 for Derived Asset pools? (Leaving Asset/Decimals/Status/StatusSince/BalanceRune/BalanceAsset as the only non-zero values, that is.)