Move `Count` to `functions-aggregate`, update MSRV to rust 1.75 #27823

Job	Run time
cargo test (macos)	10m 24s
build with wasm-pack	2m 35s
cargo check	3m 39s
Check cargo fmt	46s
cargo test (macos-aarch64)	10m 2s
Verify MSRV (Min Supported Rust Version)	6m 48s
cargo test (win64)	34m 26s
Verify Vendored Code	57s
cargo examples (amd64)	12m 26s
cargo test (amd64)	9m 40s
clippy	5m 2s
cargo test hash collisions (amd64)	9m 26s
cargo doc	3m 51s
cargo test doc (amd64)	12m 47s
cargo test datafusion-cli (amd64)	3m 53s
Run sqllogictest with Postgres runner	3m 25s
cargo test pyarrow (amd64)	2m 50s
verify benchmark results (amd64)	10m 55s
check Cargo.toml formatting	3m 0s
check configs.md is up-to-date	2m 52s
	2h 29m 44s

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