[FFL-2929] Bound Android assignment request latency

[leoromanovsky]

Motivation

Precomputed assignment requests can block an Android evaluation-context update while OkHttp waits for a slow or unavailable edge. The SDK needs a bounded default request budget without preventing applications from selecting a different budget.

Changes and Decisions

• Add assignmentRequestTimeout() and assignmentRequestRetryCount() to FlagsConfiguration.Builder.
• Use a 1,000 ms total call timeout per attempt and one retry by default. The default budget is two attempts of up to one second each.
• Apply the OkHttp call timeout to the complete request, including response body reading.
• Create a fresh OkHttp call for every attempt.
• Retry I/O failures, HTTP 408, HTTP 429, and HTTP 5xx responses.
• Do not retry other HTTP 4xx responses or non-I/O failures.
• Define retry count as retries after the first attempt. Set it to zero to disable retries.
• Use the default timeout for non-positive values and treat a negative retry count as zero.
• Preserve the existing logging, telemetry, and cached-assignment fallback after the retry budget ends.
• Update the generated public API files and SDK documentation.

Jira: FFL-2929

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.70968% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.41%. Comparing base (2dafcfa) to head (36e415d).

Files with missing lines	Patch %	Lines
...s/internal/net/PrecomputedAssignmentsDownloader.kt	91.49%	0 Missing and 4 partials ⚠️
...in/kotlin/com/datadog/android/flags/FlagsClient.kt	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3693      +/-   ##
===========================================
- Coverage    73.41%   73.41%   -0.00%     
===========================================
  Files          999      999              
  Lines        36564    36589      +25     
  Branches      6181     6190       +9     
===========================================
+ Hits         26842    26859      +17     
+ Misses        8000     7996       -4     
- Partials      1722     1734      +12     

Files with missing lines	Coverage Δ
...in/com/datadog/android/flags/FlagsConfiguration.kt	91.84% <100.00%> (+5.79%)	⬆️
...in/kotlin/com/datadog/android/flags/FlagsClient.kt	44.34% <0.00%> (-0.85%)	⬇️
...s/internal/net/PrecomputedAssignmentsDownloader.kt	92.16% <91.49%> (-4.14%)	⬇️

... and 43 files with indirect coverage changes

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