For backends which opt to set the new `BrokerdPosition.bs_mktid` field,
give (matching logic) priority to it such that even if the `.symbol`
field doesn't match the mkt currently focussed on chart, it will
always match on a provider's own internal asset-mapping-id. The original
fallback logic for `.fqme` matching is left as is.
As an example with IB, a qqq.nasdaq.ib txn may have been filled on
a non-primary venue as qqq.directedea.ib, in this case if the mkt is
displayed and focused on chart we want the **entire position info** to
be overlayed by the `OrderMode` UX without discrepancy.
Other refinements,
- improve logging and add a detailed edge-case-comment around the
`.on_fill()` handler to clarify where if a benign 'error' msg is
relayed from a backend it will cause the UI to operate as though the
order **was not-cleared/cancelled** since the `.on_cancel()` handler
will have likely been called just before, popping the `.dialogs`
entry. Return `bool` to indicate whether the UI removed-lines
/ added-fill-arrows.
- inverse the `return` branching logic in `.on_cancel()` to reduce
indent.
- add a very loud `log.error()` in `Status(resp='error')` case-block
ensuring the console yells about the order being cancelled, also
a todo for the weird msg-field recursion nonsense..
583353acb9