feat: telemetry for removed v2 interface imports (stacked on #6004)

[jam-jee]

Issue #, if available: N/A

⚠️ Stacked PR. This is based on #6004 (actionable guidance for removed v2 interfaces), not directly on master. The base branch is jam-jee:feat/v3-removed-module-guidance, so this PR's diff shows only the telemetry delta. Merge #6004 first, then this will be retargeted to master. Telemetry has nothing to instrument without the guidance code, hence the stack.

Description of changes:

Adds usage telemetry for the removed-v2-interface imports introduced in #6004 — so we can measure how often each removed interface (sagemaker.estimator, etc.) is still being imported in v3 and prioritize migration support.

• New Feature.DEPRECATED_V2_INTERFACE (code 21); the specific removed module name travels in x-extra, so one feature code covers all removed interfaces and you slice by module.
• Removed imports have no sagemaker_session, so a session-less emit resolves account id + region best-effort and sends the same field to the same endpoint as the existing session-based emitter (no new data category — this is the same account-id field already collected on normal operations).
• Strictly best-effort: hard time-bounded via a daemon worker (a slow/hung STS/S3 call can never delay the ModuleNotFoundError), once per module per process, and never raises.
• Opt-out honors the standard TelemetryOptOut SDK-defaults config (loaded session-lessly via load_sagemaker_config()), with SAGEMAKER_DEPRECATION_TELEMETRY_OPT_OUT as an additional env-var fallback.
• Wired into raise_removed_in_v3 and the fallback finder via a lazily-imported, fully-guarded hook.

Testing done:

• Extends tests/unit/test_removed_v2_modules.py (+8 telemetry tests, 44 total, all pass): dedup, opt-out via config and env var, time-bounding under a simulated 5s hang, never-raises, account fallback to NotAvailable, and the end-to-end import→hook path.
• Verified end-to-end: a simulated 10s STS hang still lets the import raise in ~1.5s; a real TelemetryOptOut: true config file opts the emit out.
• black + flake8 (repo tox.ini) clean.

Merge Checklist

General

• I have read the CONTRIBUTING doc
• I certify that the changes I am introducing will be backward compatible, and I have discussed concerns about this, if any, with the Python SDK team
  • Note for reviewers: account-id resolution happens on the import path (session-less). It is consistent with the existing telemetry's data collection, opt-out is honored, and it is hard-timeout-bounded. Data-quality caveat: account id will be NotAvailable in credential-less import environments.
• I used the commit message format described in CONTRIBUTING
• I have passed the region in to all S3 and STS clients that I've initialized as part of this change. (STS client uses tight timeouts; region resolved from the boto session, default us-west-2.)
• I have updated any necessary documentation

Tests

• I have added tests that prove my feature works
• I have added unit tests as appropriate
• I have checked that my tests are not configured for a specific region or account
• I have used unique_name_from_base for integ resource names (N/A — unit tests only)
• If adding any dependency in requirements.txt files, I have spell checked and ensured they exist in PyPi (N/A — botocore.config already a transitive dep)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.