toolchain: use latest 2.0 Mariner container for bootstrap build

[anphel31]

Merge Checklist

All boxes should be checked before merging the PR (just tick any boxes which don't apply to this PR)

• The toolchain has been rebuilt successfully (or no changes were made to it)
• The toolchain/worker package manifests are up-to-date
• Any updated packages successfully build (or no packages were changed)
• Packages depending on static components modified in this PR (Golang, *-static subpackages, etc.) have had their Release tag incremented.
• Package tests (%check section) have been verified with RUN_CHECK=y for existing SPEC files, or added to new SPEC files
• All package sources are available
• cgmanifest files are up-to-date and sorted (./cgmanifest.json, ./toolkit/scripts/toolchain/cgmanifest.json, .github/workflows/cgmanifest.json)
• LICENSE-MAP files are up-to-date (./SPECS/LICENSES-AND-NOTICES/data/licenses.json, ./SPECS/LICENSES-AND-NOTICES/LICENSES-MAP.md, ./SPECS/LICENSES-AND-NOTICES/LICENSE-EXCEPTIONS.PHOTON)
• All source files have up-to-date hashes in the *.signatures.json files
• sudo make go-tidy-all and sudo make go-test-coverage pass
• Documentation has been updated to match any changes to the build system
• Ready to merge

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Summary

What does the PR accomplish, why was it needed?
Update the bootstrap toolchain code to use the latest 2.0 Mariner container image (replacing an older 1.0 image)

Change Log

• Change toolchain bootstrap code to use mcr.microsoft.com/cbl-mariner/base/core:2.0.20230609
• Change cgmanifest to reference new image
• Add tar to the container image, since it has been removed from the 2.0 base container

Does this affect the toolchain?

YES

Test Methodology

• AMD64 toolchain build: https://dev.azure.com/mariner-org/mariner/_build/results?buildId=382271&view=results
• ARM64 toolchain build: https://dev.azure.com/mariner-org/mariner/_build/results?buildId=382269&view=results