~alva/zig-bare

keep up with zig build system
move interop tests out of src
fix benchmark
add examples from go-bare
mention interoperability
add go-bare marshal union test
add go-bare marshal array/slice/map tests
add go-bare marshal struct test
add go-bare marshal optional test
port go-bare marshal tests
more go-bare tests/bug fixes
add go-bare unmarshal array/slice tests
add note about integer types
port more go-bare tests
port unmarshal tests from go-bare

This uncovered bugs in zig-bare. More tests will be ported, and all bugs
fixed.
remove symlink
remove varint.zig
remove zig compiler tests

They have become such a nuisance, and it's weird to test Zig compiler
behavior anyway.
fix `var`nings
move varint to separate library
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