chore(core/rawdb): ExampleInspectDatabase test

[qdm12]

Why this should be merged

Add an example test for InspectDatabase with options.

How this works

See example code

[qdm12]

I was initially planning to (ill-fated plan):

1. PR the previous code (long example) upstream and to main
2. Merge changes from main to feat: rawdb.InspectDatabaseOption #111 and update example to test options

The 🆕 plan:

1. PR-ing this to feat: rawdb.InspectDatabaseOption #111 directly with option testing and minimal geth code testing (i.e. not all switch cases)
2. Branched out in another branch with the previous code to PR upstream. I also changed the example to be a unit test, not an example, so it won't conflict with our example and because it was too long for an example anyway, and changed InspectDatabase to take in an io.Writer argument to test the output.

I'll comment on previous comments just for the sake of discussion and a pre-review on an upstream PR, but these conversations are unimportant so feel free to ignore too 😉

[ARR4N]

This is much easier to understand, making it "obviously" correct, which is what tests should strive to be IMO. Thanks for taking the extra time.