changefeedccl: add new table bytes metric for use in billing

[asg0451]

Add a new metric to facilitate the new changefeed billing strategy - changefeed.billing.table_bytes - This is a sum of the bytes watched per changefeed. It intentionally counts tables watched by multiple changefeeds multiple times. Also add auxiliary metrics about billing data collection: changefeed.billing.error_count (counter of errors encountered running the query that generates the table_bytes metric) and changefeed.billing.query_duration (histogram of how long the latter took). The collection of this data and emission of these metrics are gated behind an environment variable only intended to be set in ccloud: COCKROACH_ENABLE_CLOUD_BILLING_ACCOUNTING

Epic: CRDB-37031 Resolves: #121781

Release note (enterprise change): Add a new metric to facilitate the new changefeed billing strategy for usage in Cockroach Cloud.

[blathers-crl[bot]]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is 

[blathers-crl[bot]]

Your pull request contains more than 1000 changes. It is strongly encouraged to split big PRs into smaller chunks.

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[asg0451]

bors r=rharding6373,andyyang890b

[craig[bot]]

Timed out.

[asg0451]

bors r=rharding6373,andyyang890

[craig[bot]]

Build succeeded:

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

[asg0451]

blathers backport 24.1 23.2 23.1

[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 ea0a1c8912c3d5d519638f72d5d3a9a5cd219640 to blathers/backport-release-23.2-123145: 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 23.2 failed. See errors above.

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error creating merge commit from ea0a1c8912c3d5d519638f72d5d3a9a5cd219640 to blathers/backport-release-23.1-123145: 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 23.1 failed. See errors above.

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