Optimize Trivia list loading

[Jackenmen]

Description of the changes

To support listing descriptions in [p]trivia list, there's a need for further optimizations in the list loading process.

Optimizations made:

• Updated yaml.safe_load() calls to use of yaml.CSafeLoader (C implementation of the parser) when possible
• Added a flag for disabling schema validation when it is not strictly needed

The latter change is supposed to help us support retrieval of the actually needed fields without having to validate schema of the whole file, for example:

def _get_list_description(path: pathlib.Path) -> str:
    """
    Returns a trivia list description from the given path.

    Raises
    ------
    InvalidListError
        Parsing of list's YAML file failed.
    """
    trivia_dict = get_list(path, validate_schema=False)
    return str(trivia_dict.get("DESCRIPTION", ""))

@Kreusada here's an example of how we can optimally get trivia descriptions for [p]trivia list output (10 per page in this example + cache for previously generated pages) when you work on it:

import pathlib
from typing import Dict, List

from redbot.vendored.discord.ext import menus as dpy_menus
from redbot.core.utils import views
from redbot.core.utils.chat_formatting import bold, italics


class _TriviasSource(dpy_menus.ListPageSource):
    def __init__(self, items: List[pathlib.Path]):
        super().__init__(items, per_page=10)
        self._cache: Dict[int, str] = {}

    async def get_page(self, page_number: int) -> str:
        cached = self._cache.get(page_number)
        if cached is not None:
            return cached

        categories = await super().get_page(page_number)
        entries = []
        for path in categories:
            description = _get_list_description(path)
            if len(description) > 100:
                description = f"{description[:99]}\N{HORIZONTAL ELLIPSIS}"
            elif not description:
                description = italics(_("No description provided for this category."))

            entries.append(f"- {bold(path.stem)} - {description}")

        ret = "\n".join(entries)
        self._cache[page_number] = ret
        return ret

    async def format_page(
        self, view: discord.ui.View, page: views._ACCEPTABLE_PAGE_TYPES
    ) -> views._ACCEPTABLE_PAGE_TYPES:
        return page


# ...

# in `[p]trivia list` implementation:
items = self._all_lists()
menu = views.SimpleMenu(items)
menu._source = _TriviasSource(items)
await menu.start(ctx)

Have the changes in this PR been tested?

Yes

[Kreusada]

LGTM