task: add join_all method to JoinSet #10514

Job	Run time
docs	26s
clippy	30s
fmt	16s
Check README	5s
minrust	16s
basic checks	1s
compile tests with parking lot send guards	1s
Run integration tests for each feature	1s
test tokio instrumentation	1s
test tokio full	1s
test all crates in the workspace with all features	1s
test all crates in the workspace with all features and panic=abort	1s
valgrind	1s
asan	1s
check tokio full --internal-mt-counters	1s
cross-check-tier3	1s
cross-check	1s
cross-test-without-parking_lot	1s
cross-test-with-parking_lot	1s
miri	1s
semver	1s
test tokio full --unstable	1s
test tokio full --unstable --taskdump	1s
check-external-types (${{ matrix.os }})	1s
check-fuzzing	1s
build tokio for redox-os	1s
check-spelling	1s
check unexpected lints and cfgs	1s
minimal-versions	1s
build loom tests	1s
features ${{ matrix.name }}	1s
Check tokio --feature-powerset --depth 2 on i686-unknown-linux-gnu without AtomicU64	1s
Test tokio --all-features on i686-unknown-linux-gnu without AtomicU64	1s
Test hyper	1s
test tokio for wasm32-unknown-unknown	1s
Test Quinn	1s
${{ matrix.target }}	1s
build tokio for x86_64-fortanix-unknown-sgx	1s
all systems go	1s
	2m 7s

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