fix pyproject dependency groups and TOML parsing issue

[diamondburned]

This commit rearranges some dependencies in pyproject to be in their appropriate dependency groups (test, types) rather than in the main list.

Also fixed minor TOML formatting issue that caused a C++ TOML parser to fail at tool.mypy:

error: while parsing TOML: [error] toml::insert_value: table ("tool.mypy") already exists.
 --> fromTOML
     |
 126 | [[tool.mypy.overrides]]
     | ~~~~~~~~~~~~~~~~~~~~~~~ table already exists here
 ...
 134 | [tool.mypy]
     | ~~~~~~~~~~~ table defined twice

[jjk-g]

/lgtm
/approve

[k8s-ci-robot]

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This pull-request has been approved by: diamondburned, jjk-g

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