feat(medusa): Move search indexing into a separate subscriber to defer the work load (#1874)

**What**

Move the preliminary indexing action at boot time to a separate subscriber in order to defer the work load in the background and therefore to avoid increasing the load time when the number of products increase with time.

**Tests**
Add 10k products (since it is our limit, tried with 50k before getting the error limit) using 
```sal
do $$
declare
   counter integer := 0;
begin
   while counter < 10000 loop
     INSERT INTO product (id, title, description, handle, profile_id)
        (SELECT * FROM ((SELECT random(), random(), random(), random(), 'sp_01FNB9K7FXB0SZMKXD013RJYSP')) as T);
      counter := counter + 1;
   end loop;
end$$;
```
then start the server and while the server is starting, hit the search end point repeatedly 

FIXES CORE-258

Co-authored-by: Oliver Windall Juhl <59018053+olivermrbl@users.noreply.github.com>

.changeset/large-bottles-jam.md

@@ -0,0 +1,6 @@
+---
+"medusa-interfaces": patch
+"@medusajs/medusa": patch
+---
+
+Move search indexing into a separate subscriber to defer the work load