Tests

feat: add `abigen!` macro #917

Job	Run time
no-std build	2m 54s
Unix tests (ubuntu-latest, stable)	15m 56s
Unix tests (ubuntu-latest, nightly)	15m 54s
WASM tests	9m 49s
Unix tests (macos-11, stable)	15m 55s
Windows tests (stable, x86_64-pc-windows-gnu)	12m 14s
Unix tests (macos-11, nightly)	15m 52s
Windows tests (stable, x86_64-pc-windows-msvc)	21m 13s
Windows tests (nightly, x86_64-pc-windows-gnu)	21m 4s
Windows tests (nightly, x86_64-pc-windows-msvc)	21m 13s
	2h 32m 4s

Provide feedback