Performance: Preprocess classifier text with Tantivy instead of NLTK (#14127)

* Preprocesses classifier content with Tantivy instead of NLTK

Tokenizing and stemming now happen in one Rust call instead of NLTK's
Python tokenizer and per word stemming, which also removes the Redis
backed stem cache from every preprocessing call. The output matches the
NLTK pipeline closely; tokens containing digits are now stemmed, and the
English stop words follow Snowball's list.

Stemming and stop word removal apply whenever the OCR language is one of
the supported classifier languages, so PAPERLESS_ENABLE_NLTK and
PAPERLESS_NLTK_DIR are removed.

* Copies packages instead of hardlinking them in backend CI, some NLTK thing

* Adds a normalization to NFC to better fit what Tantivy expects

src/documents/tests/samples/preprocessed_content_advanced.txt

@@ -1 +1 @@
-sampl textual document content includ mani charact possibl check classifi vector hey 00 test0707 content exampl document creat 2025 06 25 digit 0123456789 punctuat english text quick brown fox jump lazi dog english stop word accent latin diacrit àâäæçéèêëîïôœùûüÿñ arab لقد قام المترجم بعمل جيد greek αλφα βήτα γάμμα δέλτα ωμέγα cyril привет как дела добро пожаловать chines simplifi 你好 世界 今天的天气很好 chines tradit 歡迎來到世界 今天天氣很好 japanes kanji hiragana katakana 東京へ行きます カタカナ ひらがな 漢字 korean hangul 안녕하세요 오늘 날씨 어때요 arab مرحب ا كيف حالك hebrew שלום מה שלומך emoji symbol µ math ₀ x² dx π 3 14159 e ρ ε₀ currenc 1 date format 25 06 2025 june 25 2025 2025年6月25日 quot french bonjour ça va quot german guten tag wie geht newlin test r n r tab ttest tspace 192 33601010101 end document
+sampl textual document content includ mani charact possibl check classifi vector hey 00 test0707 content exampl document creat 2025 06 25 digit 0123456789 punctuat english text quick brown fox jump lazi dog english stop word accent latin diacrit àâäæçéèêëîïôœùûüÿñ arab لقد قام المترجم بعمل جيد greek αλφα βήτα γάμμα δέλτα ωμέγα cyril привет как дела добро пожаловать chines simplifi 你好 世界 今天的天气很好 chines tradit 歡迎來到世界 今天天氣很好 japanes kanji hiragana katakana 東京へ行きます カタカナ ひらがな 漢字 korean hangul 안녕하세요 오늘 날씨 어때요 arab مرحبًا كيف حالك hebrew שלום מה שלומך emoji ️ symbol µ math x dx π 3 14159 e ρ ε currenc 1 date format 25 06 2025 june 25 2025 2025年6月25日 quot french bonjour ça va quot german guten tag wie geht newlin test r n r tab ttest tspace 192 33601010101 end document