Correctly parse timestamps from 1970

[jsirianni]

Description of Changes

See OTEL issue open-telemetry/opentelemetry-log-collection#414

Porting this OTEL PR open-telemetry/opentelemetry-log-collection#417

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Add a changelog entry (for non-trivial bug fixes / features)
• CI passes

[codecov]

Codecov Report

Merging #578 (61a965c) into master (3b23e5c) will decrease coverage by 1.78%.
The diff coverage is 88.28%.

@@            Coverage Diff             @@
##           master     #578      +/-   ##
==========================================
- Coverage   76.69%   74.91%   -1.78%     
==========================================
  Files         132      133       +1     
  Lines        8308    10079    +1771     
==========================================
+ Hits         6371     7550    +1179     
- Misses       1473     2058     +585     
- Partials      464      471       +7     

Impacted Files	Coverage Δ
operator/buffer/buffer.go	75.86% <ø> (-1.92%)	⬇️
operator/buffer/memory.go	71.60% <ø> (-3.74%)	⬇️
...builtin/input/aws/cloudwatch/cloudwatch_persist.go	75.00% <ø> (-6.82%)	⬇️
operator/builtin/input/azure/event_hub.go	0.00% <0.00%> (ø)
operator/builtin/input/azure/event_hub_config.go	90.91% <ø> (-1.09%)	⬇️
operator/builtin/input/file/finder.go	100.00% <ø> (ø)
operator/builtin/input/file/reader.go	53.05% <0.00%> (-5.73%)	⬇️
operator/builtin/input/http/config.go	97.56% <ø> (-0.29%)	⬇️
operator/builtin/input/journald/journald.go	58.76% <ø> (-1.83%)	⬇️
operator/builtin/input/udp/udp.go	73.49% <ø> (-1.51%)	⬇️
... and 158 more

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