fix: add fast_drop_path for droprequest (#218)

* fix: add fast_drop_database_path for droprequest

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

* fix: address review

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

* fix: change the name to force_drop_all_logical_tables

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

* fix: change it to better name and add comments

Signed-off-by: yihong0618 <zouzou0208@gmail.com>
Co-authored-by: WenyXu <wenymedia@gmail.com>

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Signed-off-by: yihong0618 <zouzou0208@gmail.com>
Co-authored-by: WenyXu <wenymedia@gmail.com>

Author: yihong0618

proto/greptime/v1/region/server.proto

@@ -106,7 +106,13 @@ message CreateRequest {
 // Same as CreateRequests, but for dropping regions.
 message DropRequests { repeated DropRequest requests = 1; }
 
-message DropRequest { uint64 region_id = 1; }
+message DropRequest { 
+  uint64 region_id = 1;
+  // Only used by Metric Engine, for fast path drop.
+  // It only works for Metric Engine, and will be ignored by other engines.
+  // If true, the Metric Engine will delete logical tables in memory, and drop the physical region eventually.
+  bool fast_path = 2;
+}
 
 message OpenRequest {
   uint64 region_id = 1;