Fix upserts containing tempids in tuples

[ash14]

PR to address #378. Not sure how dirty the implementation is for this ... but tests pass so 🤷

Cheers.

[tonsky]

Thank you for the bug report and the PR. This is an interesting problem :)

I feel that tempid resolution should not happen in resolve-upserts, but somewhere earlier, around

https://github.com/tonsky/datascript/blob/1f060c07dfad2a700a8be702802734266dcf0222/src/datascript/db.cljc#L1431-L1439

Basically, same code should run, but for all tuple values, not just for a single v.

Also, checking for being a tuple is better not by coll?, but by going to schema

https://github.com/tonsky/datascript/blob/1f060c07dfad2a700a8be702802734266dcf0222/src/datascript/db.cljc#L900-L902

[ash14]

I've updated the test case - the entity to upsert now comes first which breaks the approach I was taking with this.