Investigate adding --features bpf-entrypoint to platform tools

[buffalojoec]

Problem

We've decided to do away with the no-entrypoint feature for BPF programs, where you'd typically import another BPF program's crate by specifying { .., features = ["no-entrypoint"] }.

Instead, entrypoint will be disabled by default, and a new feature bpf-entrypoint will be the flag that enables the program's entrypoint.

This is much better developer experience for those who wish to work with program crates in their dependencies, as well as a more proper use of Rust program features - namely, the fact that features should be additive.

The issue we have now is that we have to remember to provide --features bpf-entrypoint whenever we build and invoke a program. At a minimum, that means cargo build-sbf --features bpf-entrypoint and cargo test-sbf --features bpf-entrypoint.

Solution

Consider adding this feature to the platform tools so that developers need not remember to provide this feature flag.

Imagine deploying to mainnet with no program entrypoint!