[hotfix] [metrics] Document boolean parsing and extend MetricConfigTest

[lurui1997]

What is the purpose of the change

Clarify in JavaDoc how MetricConfig#getBoolean handles numeric values (they stringify to "1" / "0", which Boolean#parseBoolean does not treat as true/false). Extend MetricConfigTest with regression cases for short/byte integers, BigInteger longs, and boolean edge cases ("1", boxed 1/0).

Brief change log

• Expanded JavaDoc on getBoolean in MetricConfig
• Added parameterized test rows in MetricConfigTest

Verifying this change

This change added tests and can be verified as follows:

• mvn -pl flink-metrics/flink-metrics-core -Dtest=MetricConfigTest test

Does this pull request potentially affect one of the following parts:

• Dependencies: no
• The public API: no (behavior unchanged; JavaDoc and tests only)
• The serializers: no
• The runtime per-record code paths: no
• Deployment or recovery: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• JavaDoc only on existing API

Made with Cursor

[lurui1997]

Behavior of getBoolean is unchanged; new rows lock in current parsing for numeric and string edge cases. If the community wants numeric 1/0 to map to booleans, that would be a separate behavior change + JIRA.

[flinkbot]

CI report:

• 3fcf3ce Azure: SUCCESS

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