Add Rowid data type and YQL key generators

[zinal]

Changelog entry

Add new Rowid primitive type (14-byte opaque key) and Rowid::* YQL generators for row/column table primary keys.

Spec: https://gist.github.com/zinal/13445422ef0c5a7cdad0c3ae9d657767
Reference Uuid generators PR: ydb-platform#45923

Changelog category

• Experimental feature

Description for reviewers

This PR proposes end-to-end support for the new Rowid data type from the pk_generation design, plus YQL generators mirroring the Uuid UDF API.

Type design

Property	Choice
Type id	NYql.NProto.Rowid = 0x1205, public Ydb.Type.ROWID
Size	Fixed 14 bytes
Byte order	Internal == external (no mixed-endian, unlike Uuid)
Text form	Base64 without padding → 19 chars (spec said 18; corrected: ceil(14*8/6)=19)
Public wire	bytes_value with length 14 (not low_128/high_128)
Storage win	Fits TCell::MaxInlineSize() and TUnboxedValuePod embedded buffer (14)

YQL API (Rowid UDF module)

Rowid::newRowKey([T1, ...]) -> Rowid
Rowid::newColumnKey([T1, ...]) -> Rowid
Rowid::newRowGroup(PFX, COUNT, [T1, ...]) -> List<Rowid>  -- PFX: Uint64 | Rowid

Optional dependency args work like RandomUuid() / Uuid PR generators.

Bit layouts (per spec):

• Row key: [12 prefix][31 ts sec][5 rand][64 rand]
• Column key: [31 ts sec][1 rand][80 rand]

What this PR wires

• Type IDs: YQL proto, public API proto, scheme NTypeIds, SDK EPrimitiveType
• Scheme type TRowid : char[14], registry, cell compare/hash
• YQL/MiniKQL: parse/format (Base64), cast table, hash/compare/equate, pack/presort, serialization, Min/Max, SQL name Rowid
• Convert paths: ydb_convert, mkql_proto, JSON/YSON/value formatting, SHOW CREATE, KQP literals
• C++ SDK: TRowidValue, parser/builder, Base64 ToString()
• UDF module + C++ sort-order UT + YQL canon tests
• Linked into ydbd

Intentionally deferred / follow-ups

• Arrow FixedSizeBinary(14) path (currently variable binary(), like DyNumber)
• Full OLAP/columnshard/export/CDC/CLI coverage parity with Uuid
• Non-C++ SDKs (Go/Python/Java) generated/hand-written bindings
• Documentation PR for user-facing docs
• Feature-flag / experimental gating if required by release process

Test plan

• ./ya make --build relwithdebinfo -tA ydb/library/yql/udfs/common/rowid/ut
• ./ya make --build relwithdebinfo -tA ydb/library/yql/udfs/common/rowid/test
• ./ya make --build relwithdebinfo -tA yql/essentials/types/rowid
• Builds for ydb_convert, mkql_proto, SDK value, JSON/YSON value paths