Remove more common lodash patterns that have native JavaScript equivalents

[jake-low]

Continuing on the theme from #2515, this PR replaces a few more common lodash-isms in the codebase with native JavaScript equivalents.

• _first(arr) and _last(arr) become arr[0] and arr[arr.length - 1]
• _indexOf(arr, elem) becomes arr.indexOf(elem)
• _isFinite(val) becomes Number.isFinite(val)
• _isBoolean(val) becomes typeof val === "boolean"
• _isFunction(val) becomes typeof val === "function" (or in cases where it was being used to check if an optional function was present before calling it, I've replaced it with the optional-chaining operator val?.())
• _isUndefined(val) becomes val === undefined
• _isArray(val) becomes Array.isArray(val)

Each type of change was made in a separate commit, so you can review them one by one if you prefer.