Remove clearpins

[hannahhoward]

Goals

fix #164

Implementation

Maybe I'm reading this code wrong but essentially:

• pins is a list of items not to delete.
• you only check this list in a prune
• instead of keeping it up to date on every block pin, just delete when you need check it.
• possible memory growth here but honestly, we're getting killed with block data cause of this and I think it'll help a lot.

[hannahhoward]

What's up with CI?

[codecov-commenter]

Codecov Report

Base: 5.00% // Head: 5.46% // Increases project coverage by +0.45% :tada:

Coverage data is based on head (3d9412f) compared to base (9cabb28). Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #165 +/- ## ========================================= + Coverage 5.00% 5.46% +0.45% ========================================= Files 15 15 Lines 1679 1666 -13 ========================================= + Hits 84 91 +7 + Misses 1590 1572 -18 + Partials 5 3 -2 ``` | [Impacted Files](https://codecov.io/gh/application-research/autoretrieve/pull/165?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=application-research) | Coverage Δ | | |---|---|---| | [blocks/randompruner.go](https://codecov.io/gh/application-research/autoretrieve/pull/165?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=application-research#diff-YmxvY2tzL3JhbmRvbXBydW5lci5nbw==) | `0.00% <0.00%> (ø)` | | | [blocks/manager.go](https://codecov.io/gh/application-research/autoretrieve/pull/165?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=application-research#diff-YmxvY2tzL21hbmFnZXIuZ28=) | `84.31% <0.00%> (+6.86%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=application-research). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=application-research)

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[rvagg]

CI looks broken this time because of azure ubuntu DNS issues by the look of it; 🤦 this is because of ffi of course.

[rvagg]

(I'm skeptical this is going to have much effect but it's worth a try and it's a good start)