perf: Avoid boxing in doubleToBigDecimal timestamp serialization

[runningcode]

📜 Description

DateUtils.doubleToBigDecimal took a boxed Double, so callers holding a primitive double timestamp autoboxed on every serialization. This:

• Changes the parameter to a primitive double.
• Consolidates four byte-identical private copies of the helper (ProfileChunk, ProfileMeasurementValue, SentrySample, SentrySpan) to route through the single DateUtils.doubleToBigDecimal.

The classes with primitive double timestamp fields (ProfileChunk, ProfileMeasurementValue, SentrySample) no longer box on each serialize. The protocol classes whose timestamps are Double (SentrySpan, SentryTransaction, SentryLogEvent, SentryMetricsEvent) unbox at the call site instead — behavior is identical, since the previous code already unboxed internally via BigDecimal.valueOf (so null handling is unchanged).

Net -16 lines (four duplicate helpers removed).

💡 Motivation and Context

Follow-up to the "Reduce boxing to improve performance" effort. Spun out of review on #5550 (SentryNanotimeDate), where this adjacent boxing site was noticed but kept out of that focused PR.

💚 How did you test it?

Existing serialization round-trip tests pass unchanged (SentryTransactionSerializationTest, SentryProfileSerializationTest, and JsonSerializerTest cases serializes profileChunk / serializes profileMeasurement / serializes profilingTraceData / serializes transaction), confirming byte-identical JSON output.

📝 Checklist

• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

None.

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.43.2 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	311.06 ms	356.56 ms	45.50 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
a416a65	295.53 ms	373.74 ms	78.21 ms
d15471f	307.28 ms	381.85 ms	74.57 ms
4c04bb8	350.71 ms	413.63 ms	62.92 ms
9e60aca	316.18 ms	345.04 ms	28.86 ms
2124a46	319.19 ms	415.04 ms	95.85 ms
46b442b	321.41 ms	339.30 ms	17.89 ms
b193867	331.08 ms	397.06 ms	65.98 ms
b6702b0	395.86 ms	409.98 ms	14.12 ms
ed33deb	312.34 ms	369.71 ms	57.37 ms
cf708bd	434.73 ms	502.96 ms	68.22 ms

App size

Revision	Plain	With Sentry	Diff
a416a65	1.58 MiB	2.12 MiB	555.26 KiB
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
4c04bb8	0 B	0 B	0 B
9e60aca	0 B	0 B	0 B
2124a46	1.58 MiB	2.12 MiB	551.51 KiB
46b442b	0 B	0 B	0 B
b193867	1.58 MiB	2.19 MiB	620.00 KiB
b6702b0	1.58 MiB	2.12 MiB	551.79 KiB
ed33deb	1.58 MiB	2.13 MiB	559.52 KiB
cf708bd	1.58 MiB	2.11 MiB	539.71 KiB