Automatically convert :has to :-abp-has on filters build

[ameshkov]

Due to AdguardTeam/ExtendedCss#149 we may have a problem with :has rules in AdGuard.

I would like to avoid pushing a hotfix to all AG products and wait until ExtCSS v2.0 is released.

I propose to modify FiltersRegistry and add some code that replaces :has( with :-abp-has( everywhere.

Here's how it should be done:

1. Modify https://github.com/AdguardTeam/FiltersRegistry/blob/master/index.js, it should look like this:

   /**
    * Replaces all occurrencies of str to repl in the build results.
    *
    * @param {String} str - string to search for in the filters.
    * @param {String} repl - repl is string to replace with.
    */
   async function replaceInFilters(str, repl) {
       // 1. Find all ".txt" files in platformsPath recursively
       // 2. Read their content
       // 3. Replace str with repl in the content
       // 4. Write the content back
   }
   
   /**
    * Compiler entry point.
    */
   async function main() {
       await compiler.compile(
           filtersDir,
           logPath,
           reportPath,
           platformsPath,
           whitelist,
           blacklist,
           customPlatformsConfig,
       );
   
       // TODO: remove this when ExtCSS v2.0 is released to all AG products.
       await replaceInFilters();
   }
   
   main();

2. Implement replaceInFilters