feat(mean_field): added dimensions, discritization, and start of eos

The full rewrite of mean_field into something maintainable is progressing. dimensions is mostly done, discritization (domain, blocks, and fields) is done, and eos is progressing quickly

tests/sandbox/eos_sandbox.cpp

@@ -0,0 +1,11 @@
+#include <print>
+
+#include "serif/eos/models/polytropic.hpp"
+#include "serif/eos/evaluation.hpp"
+#include "serif/dimensions/type_alias.hpp"
+int main() {
+    const serif::eos::models::Polytrope polytrope(1, 0.6);
+    std::println("Density: {}", serif::eos::evaluate<serif::dimensions::Density>(polytrope, serif::dimensions::SpecificEnthalpyValue{1.0}).value());
+
+
+}