Upgrade eslint, apply lint fixes, add lint github action

[ff137]

Upgraded eslint + config + prettier dependencies with the following:

npm install --save-dev eslint@latest prettier@latest eslint-config-prettier@latest eslint-plugin-import@latest eslint-config-airbnb@latest

Fixed linting errors where possible and added ignores otherwise

Added lint job to github actions

[ff137]

Running the lint script with npm run lint yields the following errors.
Some can be fixed automatically, but I'll go through these until linting passes.

$ npm run lint

> opendota-core@21.0.2 lint
> eslint . --ext .js,.jsx --ignore-path .gitignore


/root/dev/ff137/core/dev/cassandraRandom.js
  13:74  error  Parsing error: Unexpected token .

/root/dev/ff137/core/dev/cassandraTest.js
  11:58  error  Unary operator '++' used          no-plusplus
  13:22  error  Unexpected `await` inside a loop  no-await-in-loop

/root/dev/ff137/core/index.js
  15:5  error  Strings must use doublequote  quotes

...

✖ 45 problems (45 errors, 0 warnings)
  9 errors and 0 warnings potentially fixable with the `--fix` option.

[ff137]

Quite a few of those errors (such as Parsing error: Unexpected token .) are due to linter not knowing the javascript version being used. To fix that, I added the following to the .eslintrc.json:

  "parserOptions": {
    "ecmaVersion": 2023
  },

Now there are 181 problems ... 104 of which are automatically fixable.

Edit: 2021 seems to be version that supports node16 fully - later version only somewhat. But 2021 reports same number of errors

[ff137]

Ok, with the help of Cursor (VS Code with ChatGPT), I was able to fix most of the linting errors that remained.

Some nice improvements include replacing await in a loop with executing all promises concurrently. The other changes are fairly trivial.

There's a few cases where I couldn't figure out how to replace the await in a loop.
In svc/cassandraDelete.js and dev/cassandraRandom.js, there is a while(true) loop that contains await commands. No idea how to unravel that, so I'm leaving it as is.

[ff137]

So, my renaming of variables (from snake_case to camelCase) broke something in keyManagement/tests, so rolling back those changes

I notice that test are actually quite sparse in this repo (no tests for routes), so with this refactoring it may be worthwhile if I include some more tests to make sure I didn't break anything else with the linting changes.

I guess I can only get around to that soonTM, so I'll leave PR as draft for time being

[howardchung]

I'm going to revisit eslint later--I think typescript helps us catch most of the important kinds of errors