[TASK-293] Builder pattern, cleanup, consistent API

[fresh-borzoni]

Summary

closes #293

• Align CPP Table API with Java/Rust builder pattern
• Rename Connection::Connect to Connection::Create to align with Java's createConnection

API changes

Connection

Connection::Connect(addr, conn) -> Connection::Create(addr, conn)

Append

table.NewAppendWriter(writer) -> table.NewAppend().CreateWriter(writer)

Upsert

table.NewUpsertWriter(writer)-> table.NewUpsert().CreateWriter(writer)
table.NewUpsertWriter(writer, names) -> table.NewUpsert().PartialUpdateByName(names).CreateWriter(writer)
table.NewUpsertWriter(writer, indices) -> table.NewUpsert().PartialUpdateByIndex(indices).CreateWriter(writer)

Lookup

table.NewLookuper(lookuper) -> table.NewLookup().CreateLookuper(lookuper)

Rust FFI consolidation

[fresh-borzoni]

@luoyuxia @leekeiabstraction PTAL 🙏

[Copilot]

Pull request overview

This PR aligns the C++ bindings’ Table/Connection APIs with the Java/Rust-style builder pattern, while consolidating Rust FFI entrypoints (scanner/upsert) to reduce surface area and duplication.

Changes:

• Introduce TableAppend / TableUpsert / TableLookup builder-style APIs (NewAppend/NewUpsert/NewLookup) and update examples accordingly.
• Rename Connection::Connect to Connection::Create to match other languages’ naming.
• Consolidate Rust FFI scanner creation into create_scanner(...) and upsert writer creation into create_upsert_writer(...).

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
bindings/cpp/src/table.cpp	Implements new C++ builder objects for append/upsert/lookup and routes scan creation through consolidated FFI.
bindings/cpp/src/lib.rs	Consolidates FFI methods (create_scanner, create_upsert_writer) and refactors Table internals to reuse fluss_table().
bindings/cpp/src/connection.cpp	Renames connection factory from Connect to Create and small include/format cleanup.
bindings/cpp/include/fluss.hpp	Exposes new builder classes and updates the public C++ API accordingly.
bindings/cpp/examples/kv_example.cpp	Updates example usage to new builder APIs + Connection::Create.
bindings/cpp/examples/example.cpp	Updates example usage to new builder APIs + Connection::Create.
bindings/cpp/examples/admin_example.cpp	Updates example usage to Connection::Create.

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[fresh-borzoni]

Addressed comments