@deephaven/utils - errors when installing in vscode extension

[bmingles]

I attempted to install @deephaven/utils in the vscode-deephaven extension and get a number of errors:

It looks like there are at least 2 classes of errors here:

• Incompatible CustomEvent type (presumably due to differences in TypeScript version or tsconfig target)
• References to jest. This dependency is not declared in package.json. We may also want to remove the dependency on jest from @deephaven/utils altogether since not all consumers would be using jest as their testing framework.