scpb: ensure IndexZoneConfig fields do not overlap

[annrpom]

In #134522, we added a fix to ensure that we cleaned up backrefs properly for our IndexZoneConfig element, but in doing so, we created an overlap of field ID 3 between v24.2+. This patch ensures that we do not re-use the same field ID for a different field in our IndexZoneConfig element by marking it as reserved.

Fixes: #133003 Fixes: #135807

Release note: None

[cockroach-teamcity]

This change is 

[Dedej-Bergin]

-- commits line 12 at r1: Do we need to add a Fixes: #134934

Also?

[Dedej-Bergin]

-- commits line 12 at r1:

Previously, Dedej-Bergin (Bergin Dedej) wrote…

Do we need to add a Fixes: #134934 Also?

Fixes: #134934

[annrpom]

TFTRs! ('-')7

bors r+

[craig[bot]]

Build succeeded:

• docker_image_amd64
• acceptance
• unit_tests
• linux_amd64_fips_build
• linux_arm64_build
• macos_amd64_build
• lint
• local_roachtest_fips
• linux_amd64_build
• local_roachtest
• windows_build
• examples_orms
• macos_arm64_build
• check_generated_code

[blathers-crl[bot]]

Based on the specified backports for this PR, I applied new labels to the following linked issue(s). Please adjust the labels as needed to match the branches actually affected by the issue(s), including adding any known older branches.

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Issue #135807: branch-release-24.3.

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_{:owl: Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[blathers-crl[bot]]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from d0d3a1ef3a5c3a9bfce12ce2b215fedcf8a424de to blathers/backport-release-24.3-135933: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 24.3.x failed. See errors above.

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_{:owl: Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}