custom cargo profiles for production

[ordian]

Step towards #4311.

The testnet profile is useful for https://github.com/paritytech/devops/issues/1221.

[bkchr]

I changed the pr description, because it doesn't fixes the issue entirely. We still need to change the release build to use the new profile + mentioning it everywhere in docs etc.

[ordian]

I've reverted f1d1549 because apparently the build_type

polkadot/cli/build.rs

Lines 18 to 20 in b25f8c5

	if let Ok(profile) = std::env::var("PROFILE") {
	println!("cargo:rustc-cfg=build_type=\"{}\"", profile);
	}

is set to release even with --profile testnet.

One consideration is that with debug symbols the binary size increases significantly, which might cause some issues in CI (like https://gitlab.parity.io/parity/polkadot/-/jobs/1310366), but hopefully, we can work around them.

[ordian]

bot merge