Enable HIDDEN for all column types

[atask-g]

• Modified DdlToAvroSchemaConverter to process the HIDDEN column attribute for all column types. This was originally only restricted to generated columns.
• Added unit and integration tests to cover all supported variations.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 45.41%. Comparing base (babf762) to head (7ce5ff2). Report is 41 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1990 +/- ## ============================================ + Coverage 45.04% 45.41% +0.37% - Complexity 3601 3676 +75 ============================================ Files 835 842 +7 Lines 49684 49970 +286 Branches 5229 5261 +32 ============================================ + Hits 22378 22695 +317 + Misses 25639 25605 -34 - Partials 1667 1670 +3 ``` | [Components](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/components?src=pr&el=components&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | Coverage Δ | | |---|---|---| | [spanner-templates](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `66.71% <83.33%> (+0.58%)` | :arrow_up: | | [spanner-import-export](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `64.18% <83.33%> (+0.36%)` | :arrow_up: | | [spanner-live-forward-migration](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `75.88% <ø> (-0.30%)` | :arrow_down: | | [spanner-live-reverse-replication](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `76.65% <ø> (+0.10%)` | :arrow_up: | | [spanner-bulk-migration](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `86.37% <ø> (+0.81%)` | :arrow_up: | | [Files with missing lines](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | Coverage Δ | | |---|---|---| | [...oud/teleport/spanner/AvroSchemaToDdlConverter.java](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990?src=pr&el=tree&filepath=v1%2Fsrc%2Fmain%2Fjava%2Fcom%2Fgoogle%2Fcloud%2Fteleport%2Fspanner%2FAvroSchemaToDdlConverter.java&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform#diff-djEvc3JjL21haW4vamF2YS9jb20vZ29vZ2xlL2Nsb3VkL3RlbGVwb3J0L3NwYW5uZXIvQXZyb1NjaGVtYVRvRGRsQ29udmVydGVyLmphdmE=) | `79.86% <100.00%> (ø)` | | | [...oud/teleport/spanner/DdlToAvroSchemaConverter.java](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990?src=pr&el=tree&filepath=v1%2Fsrc%2Fmain%2Fjava%2Fcom%2Fgoogle%2Fcloud%2Fteleport%2Fspanner%2FDdlToAvroSchemaConverter.java&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform#diff-djEvc3JjL21haW4vamF2YS9jb20vZ29vZ2xlL2Nsb3VkL3RlbGVwb3J0L3NwYW5uZXIvRGRsVG9BdnJvU2NoZW1hQ29udmVydGVyLmphdmE=) | `90.86% <100.00%> (ø)` | | ... and [60 files with indirect coverage changes](https://app.codecov.io/gh/GoogleCloudPlatform/DataflowTemplates/pull/1990/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform)