Simplify spider init queries

The loading of the spider plugin causes a background thread to be created and the set of sql in storage/spider/spd_init_query.h to be run.

Running mysql_upgrade at the same time the initialization of spider is occurring can cause problems as MDEV-27068 shows.

One of the conflicts was

• ALTER TABLE proc MODIFY
• and spiders' {{ drop procedure}}

Other similar conflicts can occur on plugin and udf function installation

MDEV-19275 sql service for plugins means 10.7+ can simply this. Is it valid during initialization? Not 100% sure, but if it is, it would avoid the mariadb-upgrade conflicts.

Other simplifications are:

spider_fix_one_table looks like a simple modification of the ALTER TABLE syntax to use the column IF NOT EXISTS syntax of https://mariadb.com/kb/en/alter-table/ would negate the need for this function.

mysql.spider_fix_system_tables, a procedure with zero arguments that sets user variables could be inline. Or better, removed and use the executable comment syntax in https://mariadb.com/kb/en/comment-syntax/#executable-comment-syntax to run statements based on the server version.

Can the following be implemented another way install plugin [spider_rewrite soname 'ha_spider' (INSTALL PLUGIN has IF NOT EXISTS from 10.4)

Can the udf functions created another way?

Is there are reason (all of) this couldn't be part of mysql-upgrade? wrapped under conditional upgrade if spider is installed?