feat: Support redacting anonymous context attributes in all events

[keelerm84]

Summary

Custom-event (and migration_op) anonymous-context redaction is a server-side behavior: server-side SDKs inline the full context and must redact an anonymous context's attributes into _meta.redactedAttributes. Client-side/mobile SDKs use the current context for custom events and must not redact them (only feature events redact anonymous contexts on the client) — see sdk-test-harness #388.

Because this internal module is shared by both the server SDK and client/mobile SDKs (e.g. Android), the redaction is gated behind a new opt-in flag rather than applied unconditionally. The flag is named redactAnonymousAllEvents to match the js-core convention (js-core #1814).

Scope of this PR (internal module only)

• EventsConfiguration: new redactAnonymousAllEvents field (default false) + a full constructor overload. The existing constructors default it to false, so client/mobile consumers are unaffected and remain source-compatible.
• EventOutputFormatter: custom and migration_op events honor the flag (migration_op is only ever produced server-side). Feature-event redaction is unchanged (both client and server).
• Tests: server-behavior (flag on → redacts, single + multi kind, custom + migration), client-behavior (flag off → full context).

Follow-up (separate PR, after this releases)

Ships as a new launchdarkly-java-sdk-internal release. The server SDK then opts in via a follow-up PR that bumps launchdarklyJavaSdkInternal and sets redactAnonymousAllEvents in ComponentsImpl. That is when the server contract tests go green.

CI note

test-contract-tests builds the server SDK against the released internal, so the custom/migration anonymous-redaction contract tests remain red on this PR until the follow-up server bump — expected, not a regression. The java-sdk-internal checks (unit tests) cover this change.

Verification

• internal unit tests pass (server-behavior custom + migration, client-behavior no-redaction).
• Verified end-to-end against the local sdk-test-harness v2 @ 0317ec5 (incl. #388): with the server opting in, events/custom events/*anonymous* and migrations/redacts anonymous context attributes pass; with the flag off, the custom-event context is emitted unredacted (client behavior).

Jira: SDK-2732

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Note

Medium Risk
Changes analytics payload shape for anonymous contexts when the flag is enabled; default-off preserves current client behavior but server adopters must enable it deliberately to match harness expectations.

Overview
Adds an opt-in redactAnonymousAllEvents flag on EventsConfiguration (defaults false via existing constructors so client/mobile SDKs stay unchanged). When enabled, EventOutputFormatter redacts anonymous context attributes on custom and migration_op events—the same _meta.redactedAttributes behavior feature events already use—while identify/index and client-default custom events are unchanged.

Unit tests cover server-style redaction (single- and multi-kind) and client-style full context when the flag is off. Contract-test suppressions were added for anonymous custom/migration scenarios until the server SDK opts in in a follow-up release.

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