Changes to _seek_first_non_exhausted_acquired_lot to get highest cost lot

[debben]

Get the highest cost basis non-exhausted lot, not just the first non-exhausted. Fixes #73.

[eprbell]

Here's the summary:

• you found 2 great bugs in HIFO and submitted a fix that resolved the first one;
• I built on top of your checkins to fix the second bug (which is why I'm adding code to this PR);
• the second bug was particularly subtle: it's explained in my previous comment and it caused weird timestamp-related bugs with selection of the acquired lot under certain circumstances;
• the second bug pointed to a design flaw in the HIFO plugin: it needed to take into account both price and time when selecting acquired lots and the previous implementation only considered price. This required a partial rewrite of the HIFO plugin;
• the good news is that this provided an opportunity to simplify HIFO logic quite a bit;
• I also added your repro to test_hifo2.ods/sheet B2, so that it is now part of automated testing;
• finally I updated a number of HIFO golden files that needed refreshing after the HIFO fixes.

Could you try this out and let me know if you see any more problems, either by running it or in the code?

Again, thanks so much for reporting and helping fix such tricky bugs!

[debben]

The changes look good. I checked again against my actual 2021 data and "golden copy" pdf report from the exchange and everything is matching up.

[eprbell]

Nice, I'll go ahead and merge then. If you see any more problems, just open a new issue or PR. Thanks!

[eprbell]

I ended up refactoring the entire accounting method plugin infrastructure. Now it's possible to build a new accounting method by defining only two small methods: see the new, simplified LIFO and HIFO. This should not only make it easier to write new plugins but also less error-prone (because most of the implementation is now common and factored in the superclass).

@debben can I ask you to try your test with this new implementation? All of our tests are passing, but I'd like to make sure your test is passing as well. Thanks.

[debben]

I gave the latest of main another run against my 2021 data. The HIFO report matches my golden copy from the exchange.

[eprbell]

Great, thanks!