Multi facet selection - Record last user state

[rominail]

For the multi facets js selection, record user choice in local storage

[demiankatz]

@EreMaijala, are tests passing for you? Mine are consistently failing with:

There were 2 failures:

1) VuFindTest\Mink\SearchFacetsTest::testCheckboxFacetSelection with data set "select one (multi/single)" (['Books'], 8, true, false)
Failed asserting that 'Showing 1 - 8 results of 8' [ASCII](length: 26) contains "Showing 1 - 19 results" [ASCII](length: 22).

/usr/local/vufind/module/VuFind/tests/integration-tests/src/VuFindTest/Mink/SearchFacetsTest.php:1224

2) VuFindTest\Mink\SearchFacetsTest::testCheckboxFacetSelection with data set "select two (multi/single)" (['Books', 'Fiction'], 7, true, false)
Failed asserting that 'Showing 1 - 7 results of 7' [ASCII](length: 26) contains "Showing 1 - 19 results" [ASCII](length: 22).

/usr/local/vufind/module/VuFind/tests/integration-tests/src/VuFindTest/Mink/SearchFacetsTest.php:1224

I haven't taken a close look at why this might be -- not sure if it's a bug in the code or in the test, assuming it's not just a local glitch.

Please let me know if you need me to do more investigation on my end; I thought it would be helpful to get a second opinion before diving in too deep!

[EreMaijala]

@demiankatz Oops, I failed to consider the tests. They will obviously need to be updated because they assume multi-selection is inactive on each page load.

[demiankatz]

@rominail, are you interested in trying to figure this out, or do you want help? (I don't think you've worked with the test suite before, so I'm happy to help if you don't have time to dive in at the moment -- but if you're interested in learning, this might be a good opportunity to do so).