Add error state to icpSwapUsdPricesStore

[dskloetd]

Motivation

We loaded token prices from ICP Swap.
If this results in an error, we want to show -/- as USD values and show an error state with tooltip.
There can be 2 reasons why there is an error:

1. Fetching the ICP Swap data fails.
2. Parsing the ICP Swap data fails.

In this PR we add an extra possible "error" value to the derived store icpSwapUsdPricesStore and use it if parsing the ICP Swap data fails.

Changes

1. Set icpSwapUsdPricesStore to "error" if there is an error when parsing ICP Swap tickers or if there is an unreasonable value.

Tests

Unit tests added.

Todos

• Add entry to changelog (if necessary).
  not yet

[mstrasinskis]

Thanks!