refactor(@angular/build): lazy load beasties in critical css processor

[clydin]

Beasties and its transitive dependencies (postcss, css-select, htmlparser2, domutils, dom-serializer, and postcss parsers) were previously imported statically at the top level of the critical CSS utility.

This change converts beasties to a dynamic import that is resolved on first use within the process method of InlineCriticalCssProcessor. Deferring the loading of beasties eliminates synchronous module statting, file reading, and V8 bytecode parsing overhead from the initial CLI setup phase.

[gemini-code-assist]

Code Review

This pull request refactors the critical CSS inlining utility to dynamically import the beasties package, wrapping the BeastiesExtended class definition inside an asynchronous helper function to defer loading. Feedback on these changes highlights a potential runtime error: subclass field initializers (like warnings and errors) run after the super() constructor call. If the base class constructor triggers any logging during initialization, it will attempt to push to undefined arrays, resulting in a TypeError. To prevent this, it is recommended to use lazy-initialized getters for these arrays.