Embedded: prepared TIME parameter reports column length 16 instead of 23

Summary:
Embedded: prepared TIME parameter reports column length 16 instead of 23

Environment:
MariaDB 12.3.3 embedded (libmariadbd), Linux arm64.
Server path reports 23; embedded reports 16 for the same prepared TIME parameter.

Steps to reproduce:
1. Start the embedded server.
2. Prepare a statement that returns a TIME parameter, e.g. SELECT ? .
3. Bind a TIME value containing a sign / >24h / fractional seconds
(e.g. negative over-24h TIME with microseconds) and execute.
4. Read the result column metadata (mysql_stmt_result_metadata +
mysql_fetch_field / MYSQL_FIELD.length).

Expected:
MYSQL_FIELD.length = 23 (same as the normal server), because
MAX_TIME_FULL_WIDTH is 23 ("-DDDDDD HH:MM:SS.######").

Actual:
MYSQL_FIELD.length = 16 for embedded.
The row values themselves are identical; only the declared display width differs.

Root cause (source):
sql/sql_prepare.cc:

• non-embedded Item_param::set_param_time uses MAX_TIME_FULL_WIDTH
• embedded Item_param::set_param_time uses MAX_TIME_WIDTH
  sql/sql_const.h:
• MAX_TIME_WIDTH = 16
• MAX_TIME_FULL_WIDTH = 23
  Commit a8a757c6bb32bbf291afdf33df861127489889ab (wl#173, 2011) redefined
  MAX_TIME_WIDTH from 23 to 16, added MAX_TIME_FULL_WIDTH = 23, and updated only
  the ordinary path.

Impact:
Metadata-only. No data corruption observed. Clients that use MYSQL_FIELD.length
for buffer sizing or display width may truncate the value.

Proposed fix:
In the embedded set_param_time call, use MAX_TIME_FULL_WIDTH instead of
MAX_TIME_WIDTH (one line).

Workaround:
Clients can ignore the declared length and use the actual row length.