Switchable tokenizer (#776)

* [REFACTORING]Rename whitespace_tokenizer to tag_tokenizer for
registration

Name representing its purpose is preferred.

* Add lindera-tantivy to plume-model's dependencies

* Install lindera-tantivy

* Add SearchTokenizerConfig struct

* Add search tokenizers to config option

* Use CONFIG for tokenizers

* Use enum to hold tokenizer config instead of initializing on config phase

* Use guard instead of duplicate default values

* Use as_deref() instead of guard

* Move SearchTokenizer from plume-models to plume-models::search::tokenizer

* Rename SearchTokenizer to TokenizerKind

* Define SearchTokenierConfig::determine_tokenizer()

* Use determine_tokenizer in SearchTokenizerConfig::init()

* Pass tokenizer config to Searcher methods

* Add LowerCase filter to Lindera tokenizer

* Add test for Lindera tokenizer

* Define SEARCH_LANG env to specify tokenizers set

* Run cargo fmt

* Make Lindera tokenizer optional

* Fix typos

src/main.rs

@@ -98,7 +98,7 @@ Then try to restart Plume.
     let workpool = ScheduledThreadPool::with_name("worker {}", num_cpus::get());
     // we want a fast exit here, so
     #[allow(clippy::match_wild_err_arm)]
-    let searcher = match UnmanagedSearcher::open(&CONFIG.search_index) {
+    let searcher = match UnmanagedSearcher::open(&CONFIG.search_index, &CONFIG.search_tokenizers) {
         Err(Error::Search(e)) => match e {
             SearcherError::WriteLockAcquisitionError => panic!(
                 r#"