Update .clang-format import groups order

[tweksteen]

Match the import order to the style guide[1]. This is based on art/.clang-format.

[1] https://source.android.com/docs/setup/contribute/code-style#order-import-statements

Test: repo upload .
Change-Id: Ifd5c45fce2e20adf818d1cf03637f07b10786122

[tweksteen]

We might want to add a step to Gradle to run clang-format as part of CI (I don't think this is done yet, but I might be wrong). One option is to use Spotless with clangFormat(). Let me know if that something you'd consider and I can create a bug to track that. Thanks.

[prbprbprb]

The problem is that all the old code is formatted to the wrong standard, so if we auto-run clang-format then every time we touch a file, it'll get reformatted and break the git blame history.

[tweksteen]

Spotless has a configuration option ("ratchet") exactly for that purpose: https://github.com/diffplug/spotless/blob/main/plugin-gradle/README.md#how-can-i-enforce-formatting-gradually-aka-ratchet

It will only report a formatting issue on the diff (and nothing else).

[prbprbprb]

Ah, that sounds promising then!