docs: complete grouping search SDK examples for v3.0.x

[liyun95]

Complete the grouping-search examples: add Java, Node.js, Go, REST, and C++ for scalar-field group ordering, and add C++ examples and language tabs for basic grouping search and group-size configuration. All three sections now include C++ examples.

The ordering examples use the same category, price, and rating fields and ascending group-head price as the Python example. The basic C++ examples include the required headers, reuse the connection status variable, and handle connection, search, and result-conversion failures. A stray quote in the ordering introduction is also removed.

Validation:

• Ordering examples: Java, Node.js, Go, REST, and C++ passed compilation/syntax checks and equivalent live tests on an existing Zilliz Cloud on-demand cluster, matching the Python baseline (4 groups of 3 entities, group-head prices 10/20/30/40).
• Basic grouping and group-size C++ examples: compiled with SDK 3.0.2 and tested on an existing Zilliz Cloud cluster using the documented 10-row dataset. Results matched Python: 3 groups, and 5 groups with 9 entities respectively. Temporary test collections were removed.
• Repository link checker and whitespace checks passed. Live validation used Zilliz Cloud; no standalone Milvus server was tested.

Preview tracking: #3639 contains the ordering examples and is merged. #3641 adds the remaining C++ examples. Merge #3641 and verify the preview before merging this v3.0.x PR.

[sre-ci-robot]

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