Compile multiple contracts in single module.

[g-r-a-n-t]

What was wrong?

We were only able to compile the first contract in a module.

How was it fixed?

• Updated the compiler module internals and API to handle multiple contracts.
• Updated the contract testing harness and added a test for a module with two separate contracts.
• Updated the CLI. We now write the following to the output directory:

output
|-- Bar
|   |-- Bar.bin
|   |-- Bar_abi.json
|   `-- Bar_ir.yul
|-- Foo
|   |-- Foo.bin
|   |-- Foo_abi.json
|   `-- Foo_ir.yul
|-- module.ast
`-- module.tokens

To-Do

• OPTIONAL: Update Spec if applicable

• Add entry to the release notes (may forgo for trivial changes)

• Clean up commit history

[codecov-io]

Codecov Report

Merging #197 (96c5a10) into master (98f20e2) will decrease coverage by 0.46%.
The diff coverage is 27.50%.

@@            Coverage Diff             @@
##           master     #197      +/-   ##
==========================================
- Coverage   77.96%   77.50%   -0.47%     
==========================================
  Files          45       47       +2     
  Lines        3300     3308       +8     
==========================================
- Hits         2573     2564       -9     
- Misses        727      744      +17     

Impacted Files	Coverage Δ
compiler/src/abi/elements.rs	67.34% <ø> (-7.31%)	⬇️
compiler/src/abi/mod.rs	0.00% <0.00%> (ø)
compiler/src/lib.rs	0.00% <0.00%> (ø)
compiler/src/yul/mod.rs	0.00% <0.00%> (ø)
semantics/src/errors.rs	4.54% <0.00%> (-0.22%)	⬇️
compiler/src/abi/builder.rs	90.74% <78.57%> (+0.08%)	⬆️
compiler/src/abi/utils.rs	71.42% <0.00%> (-10.39%)	⬇️
semantics/src/traversal/expressions.rs	69.95% <0.00%> (-3.61%)	⬇️
semantics/src/traversal/functions.rs	35.59% <0.00%> (-2.51%)	⬇️
semantics/src/namespace/events.rs	92.30% <0.00%> (-2.14%)	⬇️
... and 11 more

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[cburgdorf]

Looks good. One question I have is whether this removes support for generating YUL code when the YUL code is faulty which would be a bit sad since I find it quite helpful during development.

E.g. with the current compiler one can compile fe foo.fe --emit yul even if fe foo.fe wouldn't work because the yul -> binary compilation errors. This is helpful to generate and inspect the faulty YUL code that leads to the compilation failure.