Remove `sendDefaultPii` in v9

[adinauer]

Description

Remove the deprecated sendDefaultPii option from the Java and Android SDKs in version 9. Data Collection becomes the only SDK-level control for data collected automatically by supported integrations.

sendDefaultPii was deprecated in 8.x after dataCollection shipped. The SDK and documentation warn that it will be removed in v9. This issue tracks the complete removal so no legacy configuration surface, fallback behavior, sample, or active documentation remains.

SDK work

• Remove SentryOptions.isSendDefaultPii(), setSendDefaultPii(...), and the backing field.
• Remove the corresponding ExternalOptions property and merge behavior.
• Remove all configuration keys:
  • send-default-pii / SENTRY_SEND_DEFAULT_PII
  • Spring Boot sentry.send-default-pii
  • Android manifest io.sentry.send-default-pii
  • @EnableSentry(sendDefaultPii = ...) in Spring, Spring Jakarta, and Spring 7
• Remove the v8 compatibility bridge from DataCollectionResolver. When Data Collection isn't explicitly configured, use the v9 Data Collection defaults instead of legacy sendDefaultPii behavior.
• Remove remaining direct reads, deprecation suppressions, and fallback-specific code from integrations and utilities.
• Replace the remaining compatibility exceptions:
  • Logback must use includeUnencodedMessage exclusively for original templates and parameters.
  • Decide and implement the v9 behavior for OpenTelemetry-derived sensitive HTTP headers, which still depend on sendDefaultPii in v8.
• Update Java/Android/Spring samples to use Data Collection or the narrower integration-specific option.
• Regenerate API dumps and remove the deleted public API entries.
• Update and add tests for v9 defaults, removed configuration surfaces, and integration behavior.
• Add the breaking change and migration guidance to CHANGELOG.md and the v8-to-v9 migration documentation.

Documentation work

In getsentry/sentry-docs:

• Remove the Java and Android sendDefaultPii option entries from current v9 documentation.
• Remove active Java/Android references that direct users to or describe fallback behavior for sendDefaultPii.
• Document Data Collection as the sole replacement, including the behavior change when no Data Collection fields are configured.
• Document the Logback and OpenTelemetry migration outcomes.
• Keep historical migration and versioned v8 documentation accurate rather than rewriting old behavior.
• Audit downstream wrapper documentation separately where the wrapper still exposes the legacy option.

Acceptance criteria

• A production-code search finds no sendDefaultPii, isSendDefaultPii, send-default-pii, or SEND_DEFAULT_PII compatibility path in the v9 SDK.
• Current Java and Android samples and documentation no longer configure or recommend the removed option.
• The v8-to-v9 migration guide explains how to preserve restrictive v8 behavior with explicit Data Collection settings.
• Data Collection defaults and every former compatibility exception have explicit test coverage.

Related:

• Data Collection implementation: feat(core): Data Collection #5759
• Deprecation: feat(core): Deprecate sendDefaultPii #6158
• Initial Data Collection docs: docs(java): Document Data Collection controls sentry-docs#19401
• Removal warning docs: docs(java): Warn about sendDefaultPii removal sentry-docs#19598

[linear-code]

JAVA-744