Create dolt_help system table

[milogreg]

Created the dolt_help system table. This table is meant to store documentation for system tables, procedures, functions, and variables. Currently dolt_help is only populated with documentation for procedures, and only procedures that have equivalent CLI commands.

Part of #7984

[zachmu]

This is the right idea, but it's missing a few things. Check out the difference between the command line and sql output here:

select arguments from dolt_help where target = 'dolt_add';
+-------------------------------------------------------------------------------------------------------------------------------------+
| arguments                                                                                                                           |
+-------------------------------------------------------------------------------------------------------------------------------------+
| {"table": "Working table(s) to add to the list tables staged to be committed. The abbreviation '.' can be used to add all tables."} |
+-------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

v. command line:

% dolt add --help
NAME
        dolt add - Add table contents to the list of staged tables

SYNOPSIS
        dolt add [<table>...]

DESCRIPTION

        This command updates the list of tables using the current content found in the working root, to prepare the content staged for the next commit. It adds the current content of existing
        tables as a whole or remove tables that do not exist in the working root anymore.

        This command can be performed multiple times before a commit. It only adds the content of the specified table(s) at the time the add command is run; if you want subsequent changes
        included in the next commit, then you must run dolt add again to add the new content to the index.

        The dolt status command can be used to obtain a summary of which tables have changes that are staged for the next commit.

OPTIONS
        <table>
          Working table(s) to add to the list tables staged to be committed. The abbreviation '.' can be used to add all tables.

        -A, --all
          Stages any and all changes (adds, deletes, and modifications) except for ignored tables.

        -f, --force
          Allow adding otherwise ignored tables.

        -p, --patch
          Interactively select changes to add to the staged set.

So relative to the CLI, this is missing:

• options (flags)
• synopsis
• <table> formatting for arguments

[zachmu]

Best practice here is to use a pointer for the receiver type and not the fields

[zachmu]

This is missing all the options (flags)

[zachmu]

Would call this name instead

[zachmu]

Probably want a synopsis column in here for example usage, like the CLI help