[fix][fn] Unwrap type from CompletableFuture when getting function's type args

[jiangpengcheng]

Fixes #22067

Main Issue: #xyz

PIP: #xyz

Motivation

When inferring function type args, it doesn't unwrap the CompletableFuture type

Modifications

unwrap the CompletableFuture type for the output

Verifying this change

• [x] Make sure that the change passes the CI checks.

• [x] This change added tests and can be verified as follows:

(example:)

• *Added unittests in org.apache.pulsar.functions.utils.FunctionCommonTest#testGetFunctionTypes

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

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• [ ] Dependencies (add or upgrade a dependency)
• [ ] The public API
• [ ] The schema
• [ ] The default values of configurations
• [ ] The threading model
• [ ] The binary protocol
• [ ] The REST endpoints
• [ ] The admin CLI options
• [ ] The metrics
• [ ] Anything that affects deployment

Documentation

• [ ] doc
• [ ] doc-required
• [x] doc-not-needed
• [ ] doc-complete

Matching PR in forked repository

PR in forked repository: https://github.com/jiangpengcheng/pulsar/pull/26

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