fix(idempotency): transform private class fields

[dreamorosi]

Description of your changes

This PR modifies the base tsconfig.json file used to transform our source code to ESM builds so that private class fields are downleveled correctly.

As described at length in the linked issue, the combination of the setting noEmitHelpers: true with the target being set to ES2021 (Node.js 16) caused an unexpected behavior that led to runtime errors for those customers who use ESM bundles with the Idempotency utility.

The bug was introduced due to a potentially incorrect assumption that since the feature is stated to be supported for Node.js 14+, we wouldn't need to emit specific helpers to polyfill it. Based on this, I assumed that setting noEmitHelpers to true would be fine since our target version in the same config is Node.js 16.

Besides the incorrect assumption, or a potential odd behavior (or even bug) in tsc, another real issue is that we didn't have integration tests running on the ESM build, which led us to not detect this until today.

This PR doesn't add any test, but we'll prioritize the action and address it as soon as possible within this or next iteration.

Related issues, RFCs

Issue number: #2230

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective and works
• The PR title follows the conventional commit semantics

Breaking change checklist

Is it a breaking change?: NO

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

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