feat: implement Source trait and use it for user-defined source (#2114) #1152

Job	Run time
build-rust-amd64	5m 17s
Build binaries	1m 59s
build-rust-arm64	5m 0s
Build & push linux/amd64 and linux/arm64 (numaflow)	2m 19s
Bom	1m 1s
Release	17s
	15m 53s

Provide feedback