LUCENE-9955: Reduced state of stored fields readers.

[jpountz]

This removes most state from stored fields readers.

#10994

[dnhatn]

Great find, LGTM.

[rmuir]

it would be great to open a followup "wish" issue at least to think about ways we might remove the stored fields and term vectors threadlocals completely? The difficult part is figuring out how to make the api easy, but i feel like it should be possible, e.g. something minimally invasive like:

// old
Document d1 = reader.doc(doc1);
Document d2 = reader.doc(doc2);
// new
var storedfields = reader.getStoredFields();
Document d1 = storedfields.doc(doc1);
Document d2 = storedfields.doc(doc2);

then the storedfields would just be garbage-collected normally like any other lucene index api. So you'd still prevent clone()/shared dictionary/whatever resources from happening per-document, but they'd happen per-query (is this good enough?)

Anyway, just worth a thought for the future. I hate making these apis difficult to use, but at the same time I don't like how trappy the threadlocals can be (especially if you arent using fixed threadpools etc).

[jpountz]

Agreed we should look into this! I opened https://issues.apache.org/jira/browse/LUCENE-9959.

[rmuir]

-1 to this code change which started all the new public classes/renaming problems