add BLAPrjnParams: AChThr and USTrace -- latter is key for eboa learning CS under curiosity

[rcoreilly]

This is needed for eboa initial basic performance.

[codecov[bot]]

Codecov Report

Patch coverage: 20.00% and no project coverage change.

Comparison is base (74e64c5) 30.10% compared to head (cedb4bf) 30.10%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #285 +/- ## ======================================= Coverage 30.10% 30.10% ======================================= Files 85 85 Lines 15335 15341 +6 ======================================= + Hits 4616 4618 +2 - Misses 10455 10459 +4 Partials 264 264 ``` | [Files Changed](https://app.codecov.io/gh/emer/axon/pull/285?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer) | Coverage Δ | | |---|---|---| | [axon/prjnparams.go](https://app.codecov.io/gh/emer/axon/pull/285?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer#diff-YXhvbi9wcmpucGFyYW1zLmdv) | `28.32% <0.00%> (-0.33%)` | :arrow_down: | | [axon/pvlv\_prjns.go](https://app.codecov.io/gh/emer/axon/pull/285?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer#diff-YXhvbi9wdmx2X3Byam5zLmdv) | `21.42% <100.00%> (+6.04%)` | :arrow_up: |

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[rcoreilly]

auto review as it works and passes tests :)