Add additional regexp function regexp_count() #31478

Job	Run time
cargo check	10m 21s
build with wasm-pack	2m 15s
cargo test (macos)	10m 1s
cargo test (macos-aarch64)	11m 35s
cargo test (win64)	42m 43s
Check cargo fmt	52s
Verify MSRV (Min Supported Rust Version)	7m 12s
Verify Vendored Code	54s
cargo test (amd64)	9m 55s
cargo test datafusion-cli (amd64)	4m 3s
cargo doc	4m 19s
clippy	5m 53s
cargo test doc (amd64)	14m 40s
cargo examples (amd64)	13m 12s
Run sqllogictest with Postgres runner	3m 40s
cargo test pyarrow (amd64)	2m 52s
verify benchmark results (amd64)	11m 50s
check Cargo.toml formatting	2m 57s
check configs.md is up-to-date	2m 41s
cargo test hash collisions (amd64)	14m 5s
	2h 56m 0s

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