14: .github,Cargo.toml: Strip release binaries by cargo-strip

From Rust 1.59, the cargo command is now able to strip a binary [1].
This can be enabled in Cargo.toml by adding a `strip = "true"` to
the `[profile.release]` section.

Adding such binary stripping support in Cargo.toml of the project,
also change the stripping process in the release workflow to the one
using `cargo-strip`, so that the AArch64 release binaries can also
be stripped.

[1] https://doc.rust-lang.org/beta/cargo/reference/profiles.html#strip

Signed-off-by: Henry Wang <Henry.Wang@arm.com>