[BUG] `amber check` should check pub functions even if they are not called

**To Reproduce**
```
git switch --detach 3d0b2a2aa5c72606850a5d00159097067ce36c68` # a commit on `staging`
cargo run -- check src/std/env.ab
```

**Expected behavior**
```
WARN Invalid escape sequence '\x'
at src/std/env.ab:84:43

83| pub fun input_confirm(prompt: Text, default_yes: Bool = false): Bool {
84| let choice_default = default_yes then " [\x1b[1mY/\x1b[0mn]" else " [y/\x1b[1mN\x1b[0m]"
85| trust {
Only these escape sequences are supported: \n, \t, \r, \0, \{, \$, \', \", \\
WARN Invalid escape sequence '\x'
at src/std/env.ab:84:43

...
```

**Actual behavior**
Nothing printed with exit code 0.

**Additional context**
I have a plan to add a GitHub Actions workflow that executes `amber check` for all amber files.