chore(deps): replace some Lodash functions with vanilla JS

[kytta]

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Heya, I have noticed that fast-csv pulls quite a lot of dependencies and got curious. I saw all of them are Lodash functions. I first wanted to propose replacing them with just Lodash (or, if you'd ask me, es-toolkit), but Jordan's reasoning in #761 made me reconsider this.

I then noticed, however, that some Lodash functions you use are way too simple and could be replaced with vanilla JS. So, I did. See also #1038

• _.isNil => == null
  • yes, two equal signs, not three. This way it's also true for undefined, which is Lodash behaviour
  • in one place, I could replace it with nullish coalescing operator
• _.isUndefined => == undefined
• _.isBoolean => typeof ... === 'boolean'
• _.isFunction => typeof ... === 'function'

This removes three dependencies from each @fast-csv/format and @fast-csv/parse. According to pkg-size, the removed packages attributed to 7.3% of the package's install size.

The replacements were taken from es-toolkit documentation, es-toolkit source code, or from common sense :) I haven't replaced other functions because they're not one-liners