Add tests and highlight issues with should_panic

[alfiedotwtf]

This PR contains tests that demonstrate inconsistencies found in #654.

Once this PR is merged, the following PRs can then be updated along with removing corresponding should_panic test attributes:

• Fix incorrect binary link target #665
• Extend finding components to plugins and executables distributed by forc #666
• Extend triple target to everything distributed by forc #667

Since #668 builds on top of the fixes in #666 and #667 and so will have conflicts and duplication, it will need to wait for the above PRs to be merged first before being mergeable.

[fuel-service-user]

LCOV of commit d66011f during CI #2074

Summary coverage rate:
  lines......: 86.3% (2466 of 2856 lines)
  functions..: 46.1% (380 of 825 functions)
  branches...: 63.1% (289 of 458 branches)

Files changed coverage rate: n/a

[JoshuaBatty]

Nice work. Just wondering if we could look at adding some helper functions to cut down on code duplication.

Something like

fn verify_toolchain_executables(cfg: &TestConfig, component: &Component, toolchain: &Toolchain) {
    let toolchain_bin_dir = cfg.toolchain_bin_dir(toolchain.name.as_str());
    for executable in &component.executables {
        assert!(
            toolchain_bin_dir.join(executable).exists(),
            "Executable not found: {}",
            executable
        );
    }
}

Probably a few places code duplication could be removed. Looks good otherwise.

[kayagokalp]

It might be better to remove (#654) from titles of the PRs before merging otherwise they will show up as:

Add tests and highlight issues with should_panic (#654) (#683) in the history which might a little confusing as none of the other commits are in that form. Otherwise looks good to me!