refactor(ses): split resolve_action by collection and factor action parsers

[vieiralucas]

Summary

• `resolve_action` used to be a single ~450-line `match (method, segs.len())` with a guard on `segs[2]` on almost every arm. It now dispatches on the top-level collection first and delegates to a per-collection helper that owns its own `(method, len)` match — same pattern as PR refactor(apigatewayv2): split resolve_action by endpoint shape #335 for ApiGatewayV2. Collections: `account`, `identities`, `configuration-sets`, `templates`, `contact-lists`, `suppression`, `custom-verification-email-templates`, `dedicated-ip-pools`, `dedicated-ips`, `multi-region-endpoints`, `import-jobs`, `export-jobs`, `tenants`, `resources`, `reputation`. Simple one-off leaf endpoints stay inline.
• Introduce a `decode_segment` helper and a `ResolvedAction` type alias so the helper signatures read cleanly.
• Split `parse_action` (v1.rs) into one parser per `ReceiptAction` variant (`parse_s3_action`, `parse_sns_action`, `parse_lambda_action`, `parse_bounce_action`, `parse_add_header_action`, `parse_stop_action`) chained via `Option::or_else`. Mirrors the shape of `receipt_action_xml` from PR refactor(ses): extract receipt_action_xml from rule_to_xml #327.
• Extract `send_bulk_destination` from `send_bulk_templated_email` so the per-destination record + `SentEmail` construction is a named function.

Test plan

• `cargo fmt`
• `cargo clippy --workspace --all-targets -- -D warnings`
• `cargo test --workspace --exclude fakecloud-e2e --exclude fakecloud-conformance`

---

Summary by cubic

Split SES v2 routing and v1 receipt action parsing into small, focused helpers to improve readability and make future changes easier. No behavior changes.

• Refactors
  • Reworked resolve_action to dispatch by top-level collection and delegate to per-collection helpers; simple leaf endpoints (e.g. outbound-emails, outbound-bulk-emails, tags, metrics/batch) stay inline.
  • Added decode_segment and a ResolvedAction type alias for clearer signatures.
  • Split v1::parse_action into per-variant parsers (parse_s3_action, parse_sns_action, parse_lambda_action, parse_bounce_action, parse_add_header_action, parse_stop_action) chained via or_else.
  • Extracted send_bulk_destination from send_bulk_templated_email to isolate per-destination record creation and SentEmail construction.

^{Written for commit 2bbe09a. Summary will update on new commits.}

[cubic-dev-ai]

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