Fix lastRequestTime being always the original request time

[obscurecat64]

Fixes #283

This fix ensures that lastRequestTime accurately reflects the timing of each retry.

Issue

The lastRequestTime value was always set to the original request time.

Root Cause

This bug was introduced during the TypeScript migration (v3.9.1 -> v4.0).

Changes

• Fixed the bug causing lastRequestTime to remain static.
• Added a new test case to cover this scenario and prevent future regressions.

Verification

Verified that the lastRequestTime value now correctly updates with each retry attempt, after the fix. All test cases remain passing.

[mindhells]

thanks a lot @obscurecat64

[gitSambhal]

thank you @obscurecat64