Perf: Memoize Render plugin's compile functions (#3915)

[agentic-sanyam]

Hey team,

This PR addresses #3915 by adding memoization to the Render plugin's compile and compileFile functions.

The original issue highlighted that repeated calls to renderFile or compile with the same input content or file path could lead to redundant template compilations, especially on larger sites or during watch mode builds. As noted in the issue, implementing similar caching can lead to significant build time improvements, so I figured this would be a great addition to the plugin.

Here's a quick rundown of the changes:

• compile function: Now uses a WeakMap-based compileCache to store and retrieve already compiled template functions. The cache key is generated from the template content and language, meaning if you compile the same string multiple times, it only gets processed once.
• compileFile function: Similarly, compileFile now leverages a WeakMap-based compileFileCache. This cache stores the compiled function along with the file's content at the time of compilation. Before returning a cached function, it performs a quick check against the current file content to ensure the cache is invalidated if the file has changed (crucial for watch mode or other file modifications).
• Both caches are scoped using the TemplateConfig object as a WeakMap key. This helps ensure proper isolation between different Eleventy instances and allows for efficient garbage collection when a config is no longer needed.

These changes should lead to a nice performance boost for sites that heavily use renderFile or compile, as it avoids re-compiling the same templates over and over.

I've also added a few new tests to TemplateRenderPluginTest.js to verify that the caching works as expected, including correctly invalidating the cache when file contents change.

Let me know what you think!

Fixes #3915

[Ryuno-Ki]

If you don't touch the assignments, you can use const over let, generally speaking.

[Ryuno-Ki]

You could pull the functions directly during the import:

Suggested change

	import fs from "node:fs";
	import { existsSync, unlinkSync, writeFileSync } from "node:fs";

[Ryuno-Ki]

Note: Account was created two days ago. The activity looks a little bit sus too me.