test: move more source tests to source_inline

[xxchan]

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What's changed and what's your intention?

• rename e2e_test/source to source_legacy, also move scripts/source to this dir, to avoid ppl adding new tests here
• move some good tests to source_inline

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[xxchan]

• test: move more source tests to source_inline #18870 👈
• test: move kafka alter source test to source_inline #18867 : 1 other dependent PR (#18749 )
• main

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[xxchan]

The diff is not nice. Reapply in multiple PRs