Replace the custum gauss-legendre quadrature in sparseir-rust by `gauss` in xprec-rs

[shinaoka]

We can use the double-double version to generate a rule and convert to a working float type.
https://github.com/tuwien-cms/xprec-rs/blob/878c9a203bdc9a9572b75c274278c15d2241cce7/src/gauss.rs

[shinaoka]

This tolerance should be made tighter to 1e-30.

https://github.com/SpM-lab/sparseir-rust/blob/main/sparseir-rust/src/gauss_tests.rs#L362