Speed up find* methods by 2x in common cases by checking the tag name first

The attached patch makes beautifulsoup twice as fast.
See function search_tag() in element.py. Edit the 3 lines.

Tested on beautifulsoup 4.9.1, lxml 4.5.2, python 3.7, windows 10.

How does this work?

find(something) iterates on the children elements, calling search_tag() to verify whether an element is a match for the filter, calling _matches() to perform the node comparison. It's basic AST tree parsing, nothing fancy.

This is horribly slow in python because it's running millions of lines of code, effectively a loop in a loop:
- Iterating through all the HTML/XML elements. Consider a bazillion elements in a large page.
- Comparing each element to the filter. Node comparison is a rather heavy recursive operation (see _matches).

If you think about how HTML is used and processed, a find("body") is going through a bazillion elements that are not a "body" hoping to find the one "body". Unfortunately the name comparison "body"==element.name is at the very end of the recursive node comparison, there's a tremendous waste of resources to get all the way down there only to notice the node doesn't match.

The patch adds an early comparison on the tag name. An element can't be a match if the name doesn't match, check for this early and abort never entering the heavy recursive comparison. (note: doesn't apply if there is a prefix on the node because prefixes affect names)

Result:

This improves search by tags, including find("tag") find_all("tag").
I suppose that's 90% of what people do with beautifulsoup so that's a massive speed improvement for the entire planet.

Let me know if you can see the patch. Note sure the attachment is working.

I have a code snippet for repro, text output showing software can run in 53% of the original time over various scenarios and screenshots of python profilers showing line by line information with bottlenecks. But I can't figure out how to attach any of that, doesn't seem to be support for attachments.

Really wish the project was on GitHub instead of this strange thing. ;)

Next:

Can probably do a similar thing with attributes.
If a search involves attributes and an element has no attributes, same thing, it's not going to match, could exit early.