Testing framework for AquaVM
Its primary features are:
1. It generates services declaratively by annotation in the comments inserted just after calls.
2. Ephemeral network keeps each node's data and incoming data queue. The network can be also generated based on peer IDs featured in the script.
3. One can explicitly add additional peers and services.
The example of the script annotations:
```
(seq
(call "peer_1" ("service" "func") [] var) ; ok=42
(call "peer_2" ("service" "func") [var]) ; err={"ret_code": 1, "result":"no towel"}
)
```
Passing this script to `air_test_framework::TestExecutor::new(...)` will create a virtual network with peers "peer_1" and "peer_2" (and any peer you provide in the `TestRunParameters`), and the particular calls will return respective values.
Please note that autogenerated services use modified service name as a side channel for finding a correct value: "..{N}" is added to each service name (two dots and serial number). Be careful with service names taken from a variable.
Many internal structures refer to trace positions; this is an important type of values. In the code, it is sometimes `u32`, sometimes `usize`. While such variables usually have "_pos" suffix, having a dedicated type does improve code with type guarantees.
Intially, a fold instruction was designed based on idea that its iterable can't expand,
so AIR was considered as a subtree. But after introducing recursive streams in #225, it's
no more a subtree, but a subgraph.
Use pooled `avm::server::AVMRunner` instances of
air_iterpreter_server.wasm to reduce tests' running time. It avoids
repeated WASM loading and compilation.
On my hardware, `cargo test --release` execution time (precompiled)
decreases from almost 6 minutes to 1.5 minutes.
