mariadb_upgrade utility failed to work when PATH variable is set on 12.3

Description

We identified an issue when running `mariadb_upgrade` with the global PATH variable set.

Example:
Set PATH variable to `nonexist_db` before running `mariadb_upgrade`. The specified PATH is a arbitrary value which doesn't exist. Then, trigger the `mariadb_upgrade`

Following error will be observed:

ERROR 1305 (42000) at line 3211: FUNCTION extract_schema_from_file_name does not exist

Root Cause

This is because `mariadb_upgrade` utility calls SQLs in `mariadb_fix_privilege_tables_sql.c `, which is generated after the build. There is one line in the file trying to execute a function in a SELECT query like this:

"USE sys;\n",

... 

  "SELECT extract_schema_from_file_name(file_name) AS table_schema,\n"

  "       extract_table_from_file_name(file_name) AS table_name,\n"

  "       SUM(count_read) AS count_read,\n"

  "       SUM(sum_number_of_bytes_read) AS sum_number_of_bytes_read,\n"

  "       SUM(sum_timer_read) AS sum_timer_read,\n"

  "       SUM(count_write) AS count_write,\n"

  "       SUM(sum_number_of_bytes_write) AS sum_number_of_bytes_write,\n"

  "       SUM(sum_timer_write) AS sum_timer_write,\n"

  "       SUM(count_misc) AS count_misc,\n"

  "       SUM(sum_timer_misc) AS sum_timer_misc\n"

It was originally targeted at `sys` database, but it was redirected to an inexistent database `nonexist_db` due to the PATH variable.

Fix proposal

Change from

SELECT extract_schema_from_file_name(file_name) AS table_schema

to

SELECT sys.extract_schema_from_file_name(file_name) AS table_schema

in `scripts/sys_schema/views/p_s/x_ps_schema_table_statistics_io.sql`, which is the source to generate `mariadb_fix_privilege_tables_sql.c `