There is FE config `infodb_support_ext_catalog`, the default is false.
Which means that the tables in `information_schema` database will not return info of external catalog.
Because if there are too many external catalogs in Doris with lots of db/tbl (like running p0 regression tests),
querying infomation_schema db will take a long time and may causing rpc timeout.
And there is an unresolved issue that if thrift rpc timeout, the BE may be crashed in ASAN mode.
So to avoid this issue(not fix yet), this PR mainly changes:
if `infodb_support_ext_catalog` is false,
1. query info of external catalog in information_schema db is not allowed, such as
show database like "external_catalog";
show tables like "xxx"
2. select * from information_schema.tbl will not contains external catalogs' info
3. For external p0 regression test pipeline, set `infodb_support_ext_catalog` to true to run the tests related to external catalog
