Add a test for accumulations happening before Glean inits

[Dexterp37]

This is lacking the fix, but highlights the problem :)

[codecov-io]

Codecov Report

Merging #370 into master will decrease coverage by 4.17%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #370      +/-   ##
============================================
- Coverage     75.21%   71.03%   -4.18%     
============================================
  Files            92       54      -38     
  Lines          5184     3739    -1445     
  Branches        633      469     -164     
============================================
- Hits           3899     2656    -1243     
+ Misses          824      706     -118     
+ Partials        461      377      -84

Impacted Files	Coverage Δ	Complexity Δ
glean-core/src/error_recording.rs	86.66% <0%> (-1.34%)	0% <0%> (ø)
glean-core/src/event_database/mod.rs	53.59% <0%> (-0.66%)	0% <0%> (ø)
glean-core/src/storage/mod.rs	94.59% <0%> (ø)	0% <0%> (ø)	⬇️
glean-core/src/lib.rs	61.9% <0%> (ø)	0% <0%> (ø)	⬇️
.../mozilla/telemetry/glean/private/UuidMetricType.kt
...ry/glean/acmigration/engines/UuidsStorageEngine.kt
...la/telemetry/glean/private/StringListMetricType.kt
...c/main/java/mozilla/telemetry/glean/Dispatchers.kt
...etry/glean/private/CustomDistributionMetricType.kt
...in/java/mozilla/telemetry/glean/utils/DateUtils.kt
... and 33 more

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[Dexterp37]

Closing in favour of #374