Fix assets planning should be compile-kind agnostic

[boozook]

Following #376

• fix assets-build-planner
• plan compile-kind agnostic
• improve build-plan cache, add resolved env vars

To reproduce:

1. prepare package with
   • lib
   • more then one bins, including main.rs as auto-target
   • some example(s)
2. run:

   cargo build -p=cargo-playdate && \
   CARGO_PLAYDATE_LOG="trace" RUST_LOG="trace" ./target/debug/cargo-playdate assets -vvv \
   --target-dir=./target-dev-test \
   -p=test-workspace-main-crate \
   --manifest-path=${PREPARED_PACKAGE_FROM_STEP_1}/Cargo.toml \
   --target=thumbv7em-none-eabihf --target=your-host-target \
   -- --examples --bins --lib # or --all-targets