Support formatting PROTO/ENUM values

[apstndb]

This PR adds support of PROTO/ENUM value formatting.

spanner> SELECT p, p.*
         FROM (
           SELECT AS VALUE NEW examples.spanner.music.SingerInfo{singer_id: 1, birth_date: "1970-01-01", nationality: "Japan", genre: "POP"}
         ) AS p;
+----------------------------------+-----------+------------+-------------+-------+
| p                                | singer_id | birth_date | nationality | genre |
| PROTO                            | INT64     | STRING     | STRING      | ENUM  |
+----------------------------------+-----------+------------+-------------+-------+
| CAESCjE5NzAtMDEtMDEaBUphcGFuIAA= | 1         | 1970-01-01 | Japan       | 0     |
+----------------------------------+-----------+------------+-------------+-------+
1 rows in set (0.15 msecs)
timestamp:            2025-01-22T01:11:22.810217+09:00
cpu time:             0.13 msecs
rows scanned:         0 rows
deleted rows scanned: 0 rows
optimizer version:    7
optimizer statistics: auto_20250120_18_51_29UTC

spanner> SET CLI_PROTO_DESCRIPTOR_FILE += "testdata/protos/singer.proto";
Empty set (0.00 sec)

spanner> SHOW LOCAL PROTO;
+-----------------------------------------+-------+------------------------+------------------------------+
| full_name                               | kind  | package                | file                         |
+-----------------------------------------+-------+------------------------+------------------------------+
| examples.spanner.music.SingerInfo       | PROTO | examples.spanner.music | testdata/protos/singer.proto |
| examples.spanner.music.CustomSingerInfo | PROTO | examples.spanner.music | testdata/protos/singer.proto |
| examples.spanner.music.Genre            | ENUM  | examples.spanner.music | testdata/protos/singer.proto |
| examples.spanner.music.CustomGenre      | ENUM  | examples.spanner.music | testdata/protos/singer.proto |
+-----------------------------------------+-------+------------------------+------------------------------+
4 rows in set (0.00 sec)

spanner> SELECT p, p.*
         FROM (
           SELECT AS VALUE NEW examples.spanner.music.SingerInfo{singer_id: 1, birth_date: "1970-01-01", nationality: "Japan", genre: "POP"}
         ) AS p;
+-------------------------------------------------------------------+-----------+------------+-------------+-------+
| p                                                                 | singer_id | birth_date | nationality | genre |
| PROTO                                                             | INT64     | STRING     | STRING      | ENUM  |
+-------------------------------------------------------------------+-----------+------------+-------------+-------+
| singer_id:1 birth_date:"1970-01-01" nationality:"Japan" genre:POP | 1         | 1970-01-01 | Japan       | POP   |
+-------------------------------------------------------------------+-----------+------------+-------------+-------+
1 rows in set (0.25 msecs)
timestamp:            2025-01-22T01:11:36.680126+09:00
cpu time:             0.2 msecs
rows scanned:         0 rows
deleted rows scanned: 0 rows
optimizer version:    7
optimizer statistics: auto_20250120_18_51_29UTC