fix(aws-cdk): remove SIGINT listener leak in TelemetrySession

[Adityaj0]

fixes #1862

Reason for this change

TelemetrySession.begin() registers a listener on the process-global SIGINT event every time it's called:

process.on('SIGINT', async () => {
  try {
    await this.end({ name: USER_INTERRUPTED_CODE, message: ABORTED_ERROR_MESSAGE });
  } catch (e: any) {
    await this.ioHost.defaults.trace(`Ending Telemetry failed: ${e.message}`);
  }
  process.exit(1);
});

Nothing ever removes it. Each closure retains the full TelemetrySession -- ioHost, the telemetry client, sanitized session info -- so every begin() call in a process that runs more than once without exiting (e.g. driving the CLI's exec() programmatically, or this repo's own in-process test suite: cli.test.ts, cli-commands.test.ts, deploy-options.test.ts, import-options.test.ts, diff-options.test.ts, ...) permanently leaks another retained object graph. Past 10 accumulated listeners you'd see Node's MaxListenersExceededWarning. It's also a latent correctness bug: if SIGINT ever fires with multiple accumulated listeners, all of them race to end() and process.exit().

Description of changes

• TelemetrySession now stores the SIGINT listener it registers in begin() on a private field.
• end() (already called on both the normal-completion path in cli.ts's .finally() and the SIGINT path itself) now removes that listener before doing anything else, so a session's listener is cleaned up exactly once regardless of which path ended it.

Testing

Added two tests to test/cli/telemetry/session.test.ts:

• begin() registers exactly one SIGINT listener, and end() removes it — asserts the delta is exactly -1.
• A repeated begin()/end() cycle test (20 iterations, simulating 20 exec() calls in one long-running host process) asserts process.listenerCount('SIGINT') returns to baseline every time, i.e. no net growth.

Full test/cli/telemetry/session.test.ts (34 tests) and test/cli/io-host/ (91 tests) suites pass. (Note: several unrelated test/cli/* suites currently fail to run locally on a fresh checkout due to a pre-existing missing-build-artifact issue -- @aws-cdk/cdk-explorer not being built and build-info.json not being generated -- unrelated to this change; verified the failures are all in that category and none mention telemetry/session.)

Checklist

• Unit tests added/updated
• Integration tests added/updated (not applicable — no new AWS resource types or cross-service interactions)
• No manual edits to generated files

---

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

[codecov-commenter]

Codecov Report

❌ Patch coverage is 52.17391% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.98%. Comparing base (37bbd4d) to head (1430ae2).

Files with missing lines	Patch %	Lines
packages/aws-cdk/lib/cli/telemetry/session.ts	52.17%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1863      +/-   ##
==========================================
+ Coverage   90.96%   90.98%   +0.02%     
==========================================
  Files          80       80              
  Lines       12257    12269      +12     
  Branches     1761     1764       +3     
==========================================
+ Hits        11149    11163      +14     
+ Misses       1071     1069       -2     
  Partials       37       37              

Flag	Coverage Δ
suite.unit	90.98% <52.17%> (+0.02%)	⬆️

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