Implement Google Cloud Storage Store

[onyedikachi-david]

WIP

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This change is 

[CLAassistant]

All committers have signed the CLA.

[onyedikachi-david]

@aaronmondal are you okay with this? so i can go ahead.

[aaronmondal]

@onyedikachi-david Generally looks like it's the right direction. Some things to be aware of:

• Please ensure that you're following our contribution guidelines and that things wiork with both Bazel and Cargo: https://www.nativelink.com/docs/contribute/guidelines, https://www.nativelink.com/docs/contribute/bazel. We have fairly strict equirements for perfect reproducibility. Without the Nix setup it'll be very hard to pass CI.
• You can generate the proto libraries by extending this: https://github.com/TraceMachina/nativelink/blob/main/nativelink-proto/BUILD.bazel.
• Tests should go into a separate file to optimize for incremental rebuilds.

[onyedikachi-david]

@onyedikachi-david Generally looks like it's the right direction. Some things to be aware of:

• Please ensure that you're following our contribution guidelines and that things wiork with both Bazel and Cargo: https://www.nativelink.com/docs/contribute/guidelines, https://www.nativelink.com/docs/contribute/bazel. We have fairly strict equirements for perfect reproducibility. Without the Nix setup it'll be very hard to pass CI.
• You can generate the proto libraries by extending this: https://github.com/TraceMachina/nativelink/blob/main/nativelink-proto/BUILD.bazel.
• Tests should go into a separate file to optimize for incremental rebuilds.

Thanks for the feedback. I should be done on or after the weekend.