MM-46871: Add remining search parameters to be escaped (#20963)

The first try wasn't exhaustive. I was planning to use
1f933263e7/store/sqlstore/post_store.go (L1738-L1748) for this
but it also contained `@` which we don't want.

In the end, I just used a separate slice for all
the characters to be escaped.

https://mattermost.atlassian.net/browse/MM-46871

```release-note
NONE
```

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/sqlstore/user_store.go

@@ -1503,8 +1503,11 @@ func generateSearchQuery(query sq.SelectBuilder, terms []string, fields []string
 		var dbSpecificTerm string
 
 		if isPostgreSQL {
-			// Escaping the : in case of a Postgres search.
-			term = strings.ReplaceAll(term, ":", "\\:")
+			// Refer to https://www.postgresql.org/docs/current/functions-textsearch.html for the list of operators.
+			for _, c := range []string{":", "(", ")", "<", "!", "|"} {
+				// Escaping the special chars in case of a Postgres search.
+				term = strings.ReplaceAll(term, c, "\\"+c)
+			}
 		}
 
 		for _, field := range fields {

store/storetest/user_store.go

@@ -2807,6 +2807,20 @@ func testUserStoreSearch(t *testing.T, ss store.Store) {
 			&model.UserSearchOptions{},
 			[]*model.User{},
 		},
+		{
+			"escape ( and )",
+			t1id,
+			"ji(bah)",
+			&model.UserSearchOptions{},
+			[]*model.User{},
+		},
+		{
+			"escape <",
+			t1id,
+			"ji(bah<",
+			&model.UserSearchOptions{},
+			[]*model.User{},
+		},
 		{
 			"wildcard search",
 			t1id,