Replace git submodule with package dependency for tree-sitter integration

[yeatse]

Some of the dependencies of my project (like Runestone) rely on the tree-sitter project directly, which leads to conflicts due to duplicated symbols. This PR tries to fix this by replacing the tree-sitter git submodule with a Swift package dependency.

Note that the tree-sitter-swift submodule remains unchanged in this PR because it is currently used only for testing purposes, and altering it would introduce unnecessary dependencies.

[mattmassicotte]

Thank you so much for this! I've been thinking about this change for a very long time myself.

It's a shame this conflict is even a thing. I'd love to find a way to share more significant infrastructure with Runestone aside from just the runtime. But, until that day comes, I think this is a good tradeoff for the sake of compatibility.

[mattmassicotte]

Ah looks like perhaps some tests still need to be updated?

[yeatse]

Ah looks like perhaps some tests still need to be updated?

Fixed

[yeatse]

Some of the tests are still failing. Let me have a look.

[mattmassicotte]

The tree-sitter package has a higher-than-required watchOS version. Lowering that will be a pain, so let's just raise it here.

[yeatse]

The tree-sitter package has a higher-than-required watchOS version. Lowering that will be a pain, so let's just raise it here.

From the documentation if we don't specify a platform requirement, the oldest deployment targets will be selected by default. So we can just remove it to keep consistency with the tree-sitter package.

[mattmassicotte]

Ah. The documentation is right! Leaving it out is fine if you don't actually rely on the implicit value. If it does matter, clients that change to a lower swift version will implicitly lower yours and cause breakage.

In general, I've found it to be a rare, but annoying compatibility issue when left blank.

[mattmassicotte]

But, I also don't want to make too much work for you. I'lll deal with that if it comes up!