contracts: Fix `seal_call` weights (#10796)

* Fix call weights

* Fix instantiate benchmark

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_contracts --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/contracts/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Remove stale and superflous comments

* `decrement_refcount` should be infallible

* Don't hardcode increment_refcount, decrement_refcount

* Rename CopyIn/CopyOut

* Fix warning in tests

Co-authored-by: Parity Bot <[email protected]>