docs: add phpdoc summaries, examples, and docs links to resource classes

[tharropoulos]

Change Summary

add phpdoc with one-line summaries, @example usage snippets, and @see docs links to every resource class in src/, mirroring the wording of the js client's jsdoc. hovering on $client->keys, $client->collections['products']->documents->import(...), etc. surfaces the right description, a runnable example, and a link to the relevant docs section. annotate the legacy analytics v1, synonyms, and synonym classes with @deprecated pointing to their replacements.

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