chore: Replace npmlog dependency in order to support Node 10+

[mydea]

This PR replaces the npmlog dependency with a super simple logger. We actually only use very limited stuff from npmlog, so we can drop this dependency, which, as far as I can tell, is the only thing blocking us from supporting node 10.

This does loose some coloring in the generated logs, but IMHO that is not that important - if we'd really want to, we can still bring this back with something like chalk.

I also downgraded eslint to 7.x, as then we can run the whole repo on node 10, which makes it easier to verify everything works there.

Closes #1391

[AbhiPrasad]

[kamilogorek]

This is a break change for logging behavior, as npmlog handles npm's loglevel config, as well as --silent and --verbose flags.
I will need to review it later, so please hold on with merging this.

[mydea]

Does it actually?

When I run this locally on master, I see logs no matter what npm loglevel I use, and no matter what flags I use:

➜  sentry-cli git:(master) npm config set loglevel warn
➜  sentry-cli git:(master) yarn                           
yarn install v1.22.19
[1/5] 🔍  Validating package.json...
[2/5] 🔍  Resolving packages...
success Already up-to-date.
$ node ./scripts/install.js
info sentry-cli Using cached binary: ~/.npm/sentry-cli/d8b881-sentry-cli-Darwin-universal
✨  Done in 0.72s.
➜  sentry-cli git:(master) node ./scripts/install.js --silent
info sentry-cli Using cached binary: ~/.npm/sentry-cli/d8b881-sentry-cli-Darwin-universal

But also TBH not quite sure how that should work.

[kamilogorek]

Ok, let's settle on bringing support down to v10 and dropping npmlog.
It's not worth to spend time on this, blocking other people, while solution is rather non-intrusive enough :)