I ran ESLint v6.0.1 locally, and ran `eslint --fix` on the `ai/petra/` directory to automatically fix all violations of the ESLint rules in our eslintrc.json file that could be automatically fixed.
In addition to the automatic fixes, this commit also makes two other changes:
1. Fix one ESLint warning that could not be automatically named. Namely the the `use-before-define` warning about
the `PETRA` variable being used in an unstable way. The previous structure for these files had some indirection with variable overrides that didn't actually work in practice (as ESLint correctly flagged). It luckily didn't cause any breakage, but also means it can be safely removed.
2. Correct indentation for commented-out code. Due to the specific way that some statements were commented out, it led to a somewhat confusing auto-indentation outcome. I've adjusted these to something that still satisfies the rule, but is arguably more readable. There was also one case in `AttackPlan#checkTargetObstruction` where I removed the commented out code as it had been commented out from the first commit it was introduced (r18257), and didn't serve an obvious purpose.
Depends on D2070.