Move INSERT query of repack.repack_trigger to C

[za-arthur]

Making INSERT query in C prevents SQL injections, which are possible if an INSERT query is passed as an argument.

Here is an example with "old" repack.repack_trigger:

CREATE EXTENSION pg_repack;
CREATE TABLE public.t1 (a int);
CREATE TABLE public.t2 (b varchar);
INSERT INTO public.t2 VALUES (current_user);
CREATE TRIGGER repack_trigger AFTER INSERT ON public.t1
FOR EACH ROW EXECUTE PROCEDURE repack.repack_trigger('INSERT INTO public.t2 VALUES (current_user)');
INSERT INTO public.t1 VALUES (1);
SELECT b FROM public.t2;
  b 
----------
 bob
 postgres 

It is possible to move repack.get_index_columns to C too. But list of columns is passed as an argument as for now for the sake of simplicity.

Additionally this commit adds funtions:

• repack.create_index_type
• repack.create_log_table
• repack.create_table

Another change is that tablespace_orig considers default tablespace of a database (issues #363, #305)

[dvarrazzo]

It looks good to me, apart from the suggestion to add a comment on the change of quoting. Thank you very much for this work 💜

[za-arthur]

Thank you @dvarrazzo for the review. I pushed my final commit. You already approved the PR, but I want to make sure that you don't mind if I will merge the PR in the current state?