Upgrade dependencies, migrate to vitest

[voliva]

We were on a quite old version of typescript, jest, etc. so I've tried to upgrade them.

However, I've found a lot of issues trying to get jest to work. Apparently their support for ESModules is still "experimental" and it's a nightmare to set up (specially with typescript in-between).

After trying for an hour I've decided to migrate it to vitest, which is way more out-of-the-box, specially with typescript support.

The only "drawback" is that we need to import the describe/it functions. In theory we don't actually need it because I've set up globals: true, because react-testing-library needs that, but I don't know how to tell typescript that these globals are available only on test files. So anyway, I think it doesn't hurt that much.

Accidentally closes #290 and #294

[codecov]

Codecov Report

Merging #303 (ff1fca7) into main (fb57cdb) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              main      #303    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           24        24            
  Lines          395      1232   +837     
  Branches        54       141    +87     
==========================================
+ Hits           395      1232   +837     

Files Changed	Coverage Δ
packages/utils/src/mergeWithKey.ts	100.00% <100.00%> (ø)

... and 21 files with indirect coverage changes

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[josepot]

Thanks a lot!