Closes  #1399 Description TBD

 … "PHP" class ( #1457 ) > [!WARNING]   > This is breaking change!  Review the description below to assess the impact on your app. Consolidates the `BasePHP`, `NodePHP`, and `WebPHP` classes into a single `PHP` class. This refactor reduces redundancy and clarifies the PHP handling process across different environments. ## Examples ### NodePHP **Before** ```ts import { NodePHP } from '@php-wasm/node'; const php = await NodePHP.load('8.0'); ``` **After** ```ts import { loadNodeRuntime } from '@php-wasm/node'; import { PHP } from '@php-wasm/universal'; const php = new PHP(await loadNodeRuntime('8.0')); ``` ### WebPHP **Before** ```ts import { WebPHP } from '@php-wasm/web'; const php = await WebPHP.loadRuntime('8.0'); ``` **After** ```ts import { loadWebRuntime } from '@php-wasm/web'; import { PHP } from '@php-wasm/universal'; const php = new PHP(await loadWebRuntime('8.0')); ``` ### Mounting **Before** ```ts php.useHostFilesystem(); // or  php.mount( '/home/users/adam/my-dir', '/my-dir-in-vfs'); ``` **After** ```ts import { NodeFSMount,  useHostFilesystem } from '@php-wasm/node'; useHostFilesystem( php ); php.mount( new NodeFSMount( '/home/users/adam/my-dir' ), '/my-dir-in-vfs' ); ``` Closes  #1399 ## Motivation First, the public API surface of all the PHP classes and interfaces is [overly complex]( #514 ). This PR is a step towards simplifying it. Second, in the [Boot Protocol]( #1398 ), PR the `bootWordPress()` function requires separate `createPHP` and `createPHPRuntime` callbacks just because Playground uses different classes in node.js and in the browser. With this PR, `createPHP` callback will no longer be needed anymore as `bootWordPress()` will just always create a `new PHP()` instance. ## Public API Changes - Removes `BasePHP`, `NodePHP`,  and `WebPHP` classes in favor of a single PHP class exported from `@php-wasm/universal` - `php.useHostFilesystem()` was removed in favor of a decoupled function `useHostFilesystem( php )` available in `@php-wasm/node`. - `PHP.mount()` signature changed from `mount( hostPath: string, vfsPath: string )` to `mount( mountable: Mountable, vfsPath: string )` - Moves WebPHPEndpoint from `@php-wasm/web` to `@php-wasm/universal` and renames it to `PHPWorker`. That class isn't specific to the web and could be easily used by Node workers. - Removes the `IsomorphicLocalPHP` interface.  The PHP class is now the source of truth for all derived worker, client, etc. implementations. - Removes the `createPhpInstance()` option from `bootWordPress( options )` in favor of always using the PHP class. - Updates to Documentation: Adjusted examples and references in the documentation to reflect the new `PHP` class. - Refactoring of Test Suites: Updated tests to work with the new class structure. ## Testing instructions Confirm all the CI checks pass – this PR includes an extensive refactor of all the tests. Heads up @wojtekn  @fluiddot  @sejas