Remove FILE self-references

[alkis]

Remove self-references from the FILE specification:

• offset and size apply only to data referenced by uri
• a byte range within the current file cannot be referenced
• drop the compression and encryption semantics this PR previously specified, so Encryption.md returns to its state on master
• leave inline values and external references unaffected

A large value that should live elsewhere in the same file is better served by out-of-band pages, which can hold it outside the page data without the FILE type defining its own compression, encryption, and addressing rules. That will be proposed separately.

This supersedes the earlier direction of this PR, which specified storage inheritance for self-references. The review threads on that approach are left in place for history — see in particular the AAD identity discussion, which is what motivated moving this into the page layer instead.

Discussion: https://lists.apache.org/thread/zrzc7t9fccg92rx3h4fw3ndw3bdo5xr7

[alkis]

Change of direction: this PR now removes FILE self-references instead of specifying their storage semantics (d022d27).

The AAD discussion is what convinced me. Making a self-referenced range a first-class encryption module meant the FILE type had to define its own compression block, its own encryption module, its own AAD identity, and its own size accounting — a parallel storage mechanism living next to pages but not being one. Every review comment here was a symptom of that: whether the range is bound to a page, what its identity is for AAD, whether the size is pre- or post-encryption, whether the decompressed size needs storing. Those questions only exist because the bytes sit outside any page while still needing page-like machinery.

Out-of-band pages answer all of them once, in the page layer, for every type rather than just FILE. A large value gets stored in a page that lives outside the normal page sequence, and it inherits compression, encryption, AAD, and size accounting from the existing page rules with nothing new to specify. I will send that as a separate proposal.

What this PR does now:

• offset and size apply only to data referenced by uri
• a byte range within the current file cannot be referenced
• Encryption.md returns to its state on master
• inline values and external references are unchanged

@rok @wgtmac @danielcweeks @brkyvz — the open threads all point at text that no longer exists, so nothing there needs an answer from you. I have left them unresolved rather than resolving them myself, since the reasoning in them is the reason for this change and worth keeping visible. The parts of your feedback that survive independently of self-references are already in: the aligned resolution table (@brkyvz) and the normative size wording (@danielcweeks).

[etseidl]

I like removing the self-reference, thanks @alkis.

[wgtmac]

I'm fine with removing self-reference. Since this is a spec change after previous vote, perhaps we need yet another vote for this?

[rok]

I like the simplification!
Minor comment about encryption.
Re: compression I suppose without ranges it's pretty straight forward.

[rok]

I'm not a fan of process, but self-references and byte ranges were formally voted on and approved as part of #585. This PR now removes that functionality and we should probably call a formal vote for it.

edit: I see @wgtmac already proposed this.

[rok]

Parquet.thrift should also be updated to reflect removal of self-reference, currently it states:

 * Annotates a group that represents a reference to a file, or to a range of
 * bytes that may be stored inline, elsewhere in this file, or in an external
 * file.

[alkis]

Thanks for catching parquet.thrift — I had only looked at the two Markdown files. Updated in ed8bb0b:

 * Annotates a group that represents a reference to a file, or to a range of
 * bytes that may be stored inline or in an external file.

I checked the rest of the file and that comment was the only place self-references were mentioned outside LogicalTypes.md and Encryption.md. No Thrift structures change in this PR.