refactor!(core): remove panics from manager storage accesses

[imrn99]

replace some expect calls from AttrStorageManager methods with warnings.

these methods already returned Options, so the only downside to this is that a None return can be both due to missing data or missing storage

Scope

• [x] Code

Type of change

• [x] Refactor

Other

• [x] Breaking change

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.61728% with 40 lines in your changes missing coverage. Please review.

Project coverage is 81.35%. Comparing base (798c5e8) to head (ff196de).

Files with missing lines	Patch %	Lines
honeycomb-core/src/attributes/manager.rs	38.46%	40 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #179 +/- ## ========================================== - Coverage 81.97% 81.35% -0.62% ========================================== Files 32 32 Lines 4538 4603 +65 ========================================== + Hits 3720 3745 +25 - Misses 818 858 +40 ```

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