zlib: switch to git source

zlib: switch to git source

Switch to the git repository source so that we can use zstd
compression algorithm to create smaller package tarball. This
patch also corrected the license file name[1] and the CPE ID[2].

[1] https://github.com/madler/zlib/commit/352cb28d12baf02863ff5d4d96be0587ced419a1
[2] https://nvd.nist.gov/products/cpe/detail/95C64A3E-A897-4D55-B74A-D2285440D164

Suggested-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Shiji Yang <yangshiji66@qq.com>
Link: https://github.com/openwrt/openwrt/pull/17880
Signed-off-by: Robert Marko <robimarko@gmail.com>