Do not enable `use_all_repos` for toolchains extension

Copybara Import from https://github.com/bazelbuild/rules_java/pull/191

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Do not enable `use_all_repos` for toolchains extension (#191)

The toolchain extension isn't internal to rules_java as users have to `use_extension` it to get a reference to `local_jdk`. They should not see a warning about not importing all the other repos, which comes with `modules.as_extension` due to its use of `use_all_repos`. Instead, just declare the extension as reproducible.

Closes #191
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COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_java/pull/191 from fmeum:fix-tidy b947cdca9a5b700ff6d67f2fafc5a46e6793297e
PiperOrigin-RevId: 634674703
Change-Id: Ia67ffc32262011ae997bdeda80dbc29ff3128264