fix(sdk-node): correct the BLRP envvar names used for BatchLogRecordProcessor config

[trentm]

PR #6325 accidentally changed a couple envvar names when moving their
usage from sdk-logs to sdk-node. The correct names, from the spec, are
OTEL_BLRP_SCHEDULE_DELAY and OTEL_BLRP_EXPORT_TIMEOUT.

Refs: #6325

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@cjihrig This also adds the PR number that you mentioned was missing at #6325 (comment)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.48%. Comparing base (aa4a7e8) to head (84234ed).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6368   +/-   ##
=======================================
  Coverage   95.48%   95.48%           
=======================================
  Files         363      363           
  Lines       11564    11564           
  Branches     2669     2669           
=======================================
  Hits        11042    11042           
  Misses        522      522           

Files with missing lines	Coverage Δ
...ental/packages/opentelemetry-sdk-node/src/utils.ts	95.51% <ø> (ø)

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[trentm]

@cjihrig This also adds the PR number that you mentioned was missing at #6325 (comment)

Nevermind, I now see you already did this in #6362