parseString() created a copy of the string using the wrong allocator.
Instead of using the ArenaAllocator, it was using the allocator passed
into Parser.init(). This lead to a leak as the copied string was not
freed when the ArenaAllocator was deinited.
* introduce std.json.WriteStream API for writing json
data to a stream
* add WIP tools/merge_anal_dumps.zig for merging multiple semantic
analysis dumps into one. See #3028
* add std.json.Array, improves generated docs
* add test for `std.process.argsAlloc`, improves test coverage and
generated docs
