Support migration of all PG extensions

[shubham-yb]

Since YB doesn't currently support all PG extensions, if such extensions are present in the source DB and encountered during the migration, they will error out.
List of supported extensions:

"adminpack", "amcheck", "autoinc", "bloom", "btree_gin", "btree_gist", "citext", "cube",
"dblink", "dict_int", "dict_xsyn", "earthdistance", "file_fdw", "fuzzystrmatch", "hll", "hstore",
"hypopg", "insert_username", "intagg", "intarray", "isn", "lo", "ltree", "moddatetime",
"orafce", "pageinspect", "pg_buffercache", "pg_cron", "pg_freespacemap", "pg_hint_plan", "pg_prewarm","pg_stat_monitor",
"pg_stat_statements", "pg_trgm", "pg_visibility", "pgaudit", "pgcrypto", "pgrowlocks", "pgstattuple", "plpgsql",
"postgres_fdw", "refint", "seg", "sslinfo", "tablefunc", "tcn", "timetravel", "tsm_system_rows",
"tsm_system_time", "unaccent", "uuid-ossp", "yb_pg_metrics", "yb_test_extension"

Any other extension if encountered will error out.