feat(data-collection): Add base DataCollection configuration with defaults and backfill

[sl0thentr0py]

Base branch for new DataCollection implementation to deprecate and replace send_default_pii.
Spec: https://develop.sentry.dev/sdk/foundations/client/data-collection/

Issues

• Resolves: feat(pii): Add data_collection config object, accessors & defaults #3000, feat(pii): Soft-deprecate send_default_pii + backwards-compatible mapping #3002
• Resolves: feat(pii): Add data_collection config object, accessors & defaults #3000, feat(pii): Soft-deprecate send_default_pii + backwards-compatible mapping #3002

[linear-code]

RUBY-188

RUBY-190

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[dingsdax]

❤️ Ruby is just beautiful, lgtm 👍

[solnic]

LGTM, except this one tiny formatting issue.

[sentry]

Bug: When send_default_pii is set to true, the DataCollection.backfill method incorrectly ignores the include_local_variables setting, preventing local variable capture.
_{Severity: MEDIUM}

Suggested Fix

In DataCollection.backfill, when configuration.send_default_pii is true, migrate the include_local_variables and context_lines settings from the main configuration to the new data_collection object before returning. Specifically, set data_collection.stack_frame_variables = configuration.include_local_variables and data_collection.frame_context_lines = configuration.context_lines.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: sentry-ruby/lib/sentry/data_collection.rb#L125-L126

Potential issue: When `send_default_pii` is set to `true`, the `DataCollection.backfill`
method returns a new `DataCollection` object without migrating the user's
`include_local_variables` setting. This happens due to an early return. As a result,
`data_collection.stack_frame_variables` defaults to `false`, even if the user explicitly
set `include_local_variables=true`. This causes local variables from exception frames to
be silently dropped, contrary to the user's configuration. This behavior is inconsistent
with the `send_default_pii=false` path, which correctly migrates the setting.