Core Exchange Rate (CER) of bitAssets whose BSRM is individual_settlement_to_fund or no_settlement?

For a bitAsset whose backing asset is the core asset (BTS) and BSRM is `individual_settlement_to_fund` or `no_settlement`, when price of the core asset falls, essentially there is a floor for `current_feed.settlement_price`, however, `current_feed.core_exchange_rate` does not stop falling.


In practice, when a bitAsset is globally settled, price feeder producers are asked to feed CER with `max(gs_price, feed_price * a multiplier)`. I think the same can be applied to the bitAsset whose BSRM is `individual_settlement_to_fund` or `no_settlement` too.


Start by reproducing the described core-asset price decline for a bitAsset using individual_settlement_to_fund or no_settlement, then compare current_feed.settlement_price with current_feed.core_exchange_rate. Trace the existing globally-settled CER handling and verify that the affected modes apply the proposed floor behavior without changing unrelated feeds.

Written by the indexing model from the issue text.