GH-49792: [Format][FlightSQL][C++] Add dialect-related SqlInfo codes

[tokoko]

Rationale for this change

Fills gaps in SqlInfo dialect metadata for axes that clients need when compiling SQL per-backend. Motivation and use case in #49792.

What changes are included in this PR?

• format/FlightSql.proto — four new int32_bitmask SqlInfo codes (577–580): SQL_SUPPORTED_LIMIT_OFFSET, SQL_SUPPORTED_NULLS_ORDERING, SQL_SUPPORTED_BOOLEAN_LITERAL, SQL_SUPPORTED_DATETIME_LITERAL.
• Bitmask, not scalar enum - Dialects often accept multiple forms (e.g. PostgreSQL accepts both LIMIT/OFFSET and OFFSET/FETCH; MySQL accepts both TRUE/FALSE and 1/0). Follows the existing SQL_SUPPORTED_GROUP_BY / SupportedSqlGrammar convention — enum values are bit positions;
• Enums are admittedly non-exhaustive. They are just enough to cover current use cases and leave room for other behavior.
• SQL_SUPPORTED_NULLS_ORDERING (578) is intentionally distinct from the pre-existing SQL_NULL_ORDERING (507) — the latter reports the server's default null ordering; the new flag reports whether the explicit NULLS FIRST / NULLS LAST clause is accepted.

Are these changes tested?

No behavior change.

Are there any user-facing changes?

New SqlInfo codes and supporting enums available to clients and servers. Fully backwards-compatible; no existing codes or types change.

• GitHub Issue: [Format][FlightSQL] Add dialect-related SqlInfo codes (LIMIT/OFFSET syntax, NULLS ordering clause, boolean/datetime literals) #49792

[github-actions]

⚠️ GitHub issue #49792 has been automatically assigned in GitHub to PR creator.