[WIP] Add support for external tables with qualified names #32720

Job	Run time
build with wasm-pack	2m 35s
cargo check	7m 19s
Check cargo fmt	35s
cargo test (macos)	12m 6s
cargo test (macos-aarch64)	10m 58s
Verify MSRV (Min Supported Rust Version)	7m 2s
Verify Vendored Code	45s
cargo test (win64)	47m 49s
clippy	5m 40s
cargo test hash collisions (amd64)	14m 44s
check Cargo.toml formatting	3m 3s
check configs.md is up-to-date	2m 56s
cargo doc	3m 51s
cargo test (amd64)	9m 59s
cargo test datafusion-cli (amd64)	3m 56s
cargo test doc (amd64)	15m 13s
cargo examples (amd64)	13m 19s
Run sqllogictest with Postgres runner	3m 31s
cargo test pyarrow (amd64)	2m 58s
verify benchmark results (amd64)	12m 7s
	3h 0m 26s

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