t: clean up leftover reftable test cruft

With the migration of reftable tests to the unit-tests framework,
"test-tool reftable" becomes a no-op.

Get rid of everything that uses "test-tool reftable" alongside
everything that is used to implement it.

While at it, alphabetically sort the cmds[] list in
helper/test-tool.c by moving the entry for "dump-reftable".

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>

t/helper/test-reftable.c

@@ -9,12 +9,6 @@
 #include "reftable/reftable-tests.h"
 #include "test-tool.h"
 
-int cmd__reftable(int argc, const char **argv)
-{
-	/* test from simple to complex. */
-	return 0;
-}
-
 static void print_help(void)
 {
 	printf("usage: dump [-st] arg\n\n"

t/helper/test-tool.c

@@ -26,6 +26,7 @@ static struct test_cmd cmds[] = {
 	{ "drop-caches", cmd__drop_caches },
 	{ "dump-cache-tree", cmd__dump_cache_tree },
 	{ "dump-fsmonitor", cmd__dump_fsmonitor },
+	{ "dump-reftable", cmd__dump_reftable },
 	{ "dump-split-index", cmd__dump_split_index },
 	{ "dump-untracked-cache", cmd__dump_untracked_cache },
 	{ "env-helper", cmd__env_helper },
@@ -61,9 +62,7 @@ static struct test_cmd cmds[] = {
 	{ "read-graph", cmd__read_graph },
 	{ "read-midx", cmd__read_midx },
 	{ "ref-store", cmd__ref_store },
-	{ "reftable", cmd__reftable },
 	{ "rot13-filter", cmd__rot13_filter },
-	{ "dump-reftable", cmd__dump_reftable },
 	{ "regex", cmd__regex },
 	{ "repository", cmd__repository },
 	{ "revision-walking", cmd__revision_walking },

t/helper/test-tool.h

@@ -55,7 +55,6 @@ int cmd__read_graph(int argc, const char **argv);
 int cmd__read_midx(int argc, const char **argv);
 int cmd__ref_store(int argc, const char **argv);
 int cmd__rot13_filter(int argc, const char **argv);
-int cmd__reftable(int argc, const char **argv);
 int cmd__regex(int argc, const char **argv);
 int cmd__repository(int argc, const char **argv);
 int cmd__revision_walking(int argc, const char **argv);