sql: improve env collection in stmt bundles

[yuzefovich]

This PR improves stmt bundle collection to include all session variables and cluster settings that differ from their defaults.

Fixes: #119786 Fixes: #123830.

Release note: None

[cockroach-teamcity]

This change is 

[craig[bot]]

Build succeeded:

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

[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 8ed9c312d83290f756cbb32bdda3555c8875d2a6 to blathers/backport-release-23.2-123794: 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.x failed. See errors above.

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error creating merge commit from 4e5c031a178cadbfe3f8d6cbfa744a5e070c3e43 to blathers/backport-release-24.1-123794: 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 24.1.x failed. See errors above.

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