add support for dynamic (non-static) column types in Firebird Proxy

[makssent]

Ref #33781.

Changes proposed in this pull request:

• FirebirdColumnSizeLoader now retrieves both COLUMN_SIZE and SEGMENT_SIZE for BLOB fields during metadata collection. This enables obtaining the actual length for all dynamic data types.

• In FirebirdPrepareStatementCommandExecutor, the calculated column length is stored in the columnLength variable, which is then directly passed to FirebirdReturnColumnPacket and used when forming the DESCRIBE response. As a result, the client receives accurate, real column sizes.

• During metadata loading, the computed sizes are stored in the thread-safe FirebirdSizeRegistry and synchronized at the table level. This ensures that additional queries are executed only once — during metadata collection — while subsequent accesses use the cached data.

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