Fix legacy filename migration in bundle generators

[fallintoplace]

Changes

• save generated job and pipeline configuration to the typed filename before removing the legacy file
• preserve the legacy file when writing the new configuration fails
• cover migration without --force and destination conflicts

Why

The existing migration renames <key>.yml to the typed filename before saving. Without --force, the saver then rejects the renamed destination as already existing, leaving the file moved even though generation failed.

Tests

• go test ./cmd/bundle/generate ./libs/dyn/yamlsaver
• go test ./acceptance -run "TestAccept/bundle/generate/legacy_filename_migration"

[github-actions]

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Trigger:
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Inputs:

• PR number: 6132
• Commit SHA: 83160c4a4bc9196fd785078c912365f7fec10214

Checks will be approved automatically on success.

[github-actions]

Approval status: pending

/acceptance/bundle/ - needs approval

5 files changed
Suggested: @janniklasrose
Also eligible: @denik, @andrewnester, @pietern, @lennartkats-db, @shreyas-goenka, @anton-107

/cmd/bundle/ - needs approval

Files: cmd/bundle/generate/job.go, cmd/bundle/generate/pipeline.go
Suggested: @janniklasrose
Also eligible: @denik, @andrewnester, @pietern, @lennartkats-db, @shreyas-goenka, @anton-107

_{Any maintainer (@andrewnester, @anton-107, @denik, @pietern, @shreyas-goenka, @simonfaltum, @renaudhartert-db, @janniklasrose, @lennartkats-db) can approve all areas.
See OWNERS for ownership rules.}