google.golang.org/grpc/otelgrpc: Fix for elapsedTime records an incorrect metric value

[gaiaz-iusipov]

Fix elapsedTime being recorded as (ms * 1000) in google.golang.org/grpc/otelgrpc. For example, a value of 5ms is written as 5s instead of 0.005s.

Fix #8518

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.2%. Comparing base (dbf6452) to head (8ad286c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #8509   +/-   ##
=====================================
  Coverage   82.2%   82.2%           
=====================================
  Files        179     179           
  Lines      13700   13700           
=====================================
  Hits       11265   11265           
  Misses      2033    2033           
  Partials     402     402           

Files with missing lines	Coverage Δ
...n/google.golang.org/grpc/otelgrpc/stats_handler.go	98.4% <100.0%> (ø)

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[dmathieu]

Please keep your changes atomic (a single thing per PR).

[gaiaz-iusipov]

I will remove from this PR the changes that are not related to the gRPC tooling.

[dmathieu]

For the record, this dates to #4548, before the stabilization of RPC attributes, and when the duration attribute was actually ms.
The semantic conventions upgrade missed the unit change.