Reduce memory load from DynamicStyleSheets

[andrew-k-21-12]

Check styled.StyleSheet from Kotlin Wrappers: possibly there are some updates worth to be integrated into io.github.andrewk2112.kjsbox.frontend.dynamicstylesheet.DynamicStyleSheet.

Check DynamicStyleSheet#prepareCachedRuleSet: for each particular style variant it creates and stores a separate DynamicCssHolder inside DynamicStyleSheet#dynamicHolders. This really abuses memory for no reason.

Check DynamicStyleSheet#createStyleName: it uses simple class names to generate the corresponding style names. Such approach is prone to name clashes if there are, for example, multiple DynamicStyleSheets having the same name but placed in different packages.

Try to rewrite it to keep injecting all style variants for each context immediately as it's done now but to avoid storing all corresponding DynamicCssHolders. If it's impossible to be done then try to extract shared parts of all style variants to reduce unnecessary duplication. Review and fix the issue with name clashes for generated styles.