Avoid duplication in defining tree-sitter grammar sources.

Avoid duplication in defining tree-sitter grammar sources.

* lisp/progmodes/php-ts-mode.el: Require 'html-ts-mode'.
(php-ts-mode--language-source-alist): Remove duplicate source info
for html, css, javascript, jsdoc.
(php-ts-mode-install-parsers): Install pre-defined grammars.
(php-ts-mode): Move 'require' to the top.

* lisp/textmodes/mhtml-ts-mode.el
(mhtml-ts-mode--language-source-alist): Remove variable
since 'treesit-language-source-alist' is pre-filled by
requiring 'html-ts-mode', 'css-mode', 'js'.
(mhtml-ts-mode-install-parsers): Install pre-defined grammars.

* test/infra/Dockerfile.emba: Remove 'mhtml-ts-mode'
that doesn't define own grammars.

(cherry picked from commit 815dea7b59392d83ca8f9e98d1569484aea605ad)