feat: add ability to suppress error logs

[joker23]

This PR will add the ability to suppress error logs using the same technique as some server sdks:

Now, if developers subscribes to the error event, then they will no longer see error logs. Instead
they are expected to handle errors themselves in the event callback.

basically doing the same thing as the old browser sdk

---

Note

Medium Risk
Changes how SDK errors are surfaced (emit vs log) across identify/streaming/polling and evaluation paths; risk is primarily behavioral for consumers who relied on default logger output or listener counts.

Overview
Adds opt-in suppression of internal error logging: errors are now logged only when no error listeners are registered, and otherwise are emitted to user handlers.

This introduces LDEmitter.maybeReportError and routes key error paths (invalid context in identify, streaming/polling failures in DataManager, and wrong-type flag evaluations) through it. The default LDClientImpl-level error listener is removed, and tests are updated/added to verify listener-count behavior and the new log-vs-emit semantics.

^{Reviewed by Cursor Bugbot for commit 301c447. Bugbot is set up for automated code reviews on this repo. Configure here.}

---

[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25661 bytes
Compressed size limit: 29000
Uncompressed size: 126143 bytes

[github-actions]

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 179521 bytes
Compressed size limit: 200000
Uncompressed size: 829331 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 31553 bytes
Compressed size limit: 34000
Uncompressed size: 112148 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 37131 bytes
Compressed size limit: 38000
Uncompressed size: 203288 bytes

[joker23]

@cursor review

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 301c447. Configure here.}

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 4 additional findings.

[joker23]

Closing as we will delegate to overriding the logger