fix: improve inline completion api latency measurement precision

[Will-ShaoHua]

Problem

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/now#reduced_time_precision

the precision of Date.now() might get rounded depending on browser settings. In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 2ms. You can also enable privacy.resistFingerprinting, in which case the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.

For example, with reduced time precision, the result of Date.now() will always be a multiple of 2, or a multiple of 100 (or privacy.resistFingerprinting.reduceTimerPrecision.microseconds) with privacy.resistFingerprinting enabled.

Solution

use performance.now()

basically revert changes made in #2323 to use Date.now() instead of performance.now()

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.87%. Comparing base (a908195) to head (62d8c1a).

Files with missing lines	Patch %	Lines
...p-codewhisperer/src/shared/codeWhispererService.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2406   +/-   ##
=======================================
  Coverage   61.87%   61.87%           
=======================================
  Files         261      261           
  Lines       58505    58505           
  Branches     3672     3672           
=======================================
  Hits        36199    36199           
  Misses      22235    22235           
  Partials       71       71           

Flag	Coverage Δ
unittests	61.87% <0.00%> (ø)

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