Minor syntax improvements

[mdedetrich]

This PR applies syntax improvements that are the result of Intellij's default code inspections.

Some additional notes

• Intellij recommends adding type signatures to methods/fields which are public (hence the reason behind a lot of the addition of manual type annotations). I have the suspicion that a lot of these fields should actually be private and not public (likely the reason why the types were not there in the first place). If so let me know
• Unit type annotation was added to any method that happened to return Unit (i.e. side effecting methods that don't return anything).
• The various .toSeq conversions were removed since Intellij marked them as pointless (being the same type). I am quite sure this is not going to cause issues but I would double check here just to make sure nothing odd happens
• the @tailrec annotation doesn't actually change anything in the resulting generated bytecode but it will actually confirm that scalac will correctly translation the recursion into an efficient while loop.
• There were some cases where either .close() wasn't being called, or it was but the expression wasn't in a try/finally block which would mean if there is an exception (for some reason) then the handle's wouldn't be released. I have fixed these cases.

[mdedetrich]

Intellij handily picked up the fact that the handle from source is never actually closed which actually causes a leak hence the change here. There are nicer ways of doing this i.e. using Using but this is only available in Scala 2.13

[mdedetrich]

So the latest test run is failing on VarsDirectiveSpec even though it passes fine locally with JDK8 and the previous github actions test run passed without problems (see https://github.com/lightbend/paradox/actions/runs/2101609267).

Maybe rerunning the tests should work? (although not sure why such a test would be flaky)

[johanandren]

LGTM, nice little cleanup, thanks!

[johanandren]

Oh, I missed the test failure, which is ofc not LGTM :)

[mdedetrich]

@johanandren Can you rerun the tests? The tests passed in a previous run and locally, I actually cannot replicate this error (or something really weird is going on)

[pvlugter]

Not sure what happened with the tests, rerun is fine.

[pvlugter]

👍🏼 nice cleanup