By using conditional compilation, we now support running the test suite
with Rust versions 1.83 to 1.86 again. This allows us to lower the
`rust-version` specified in the root Cargo.toml (because it was
controlling the toolchain used in CI) to 1.83, resolving #230.
This solution keeps tests operational on our MSRV while also lowering
it. It would have been unsatisfying to have an MSRV which could not
compile the tests.
`rustversion` was selected as the dependency to control the conditional
compilation since it was already a build dependency needed by
`vergen-gitcl`, so no new dependencies were added.
This should simplify how some of the code reads, as well as allowing for future
feature additions to be accomplished in a less restrictive manner. The slotmap +
Object enum pattern was kind of like a really bad ecs in a way anyway. Also I
was looking for an excuse to use an ecs.
The -displayfd argument is much friendlier to testing and is generally
more stable. As a result, omitting the display argument to the program
will result in Xwayland searching for the next available display. This
also allows integration tests to run simultaneously and when there is
already an X server running on the system.
This commit also changes how the state of the program is communicated
with integration tests (via the RunData trait).
