MySQL 5.5 in commit 177d8b0c
introduced a configuration parameter innodb_force_load_corrupted
whose purpose was to allow a corrupted table to be dropped.

Given that MDEV-11412 in MariaDB 10.5.4 aims to allow any metadata
for a missing or corrupted table to be dropped, and given that
MDEV-17567 and MDEV-25506 and related tasks made DDL operations
crash-safe, the parameter no longer serves any purpose.

Because this obscure parameter was read-only (not settable by a client),
it seems that we can simply declare it with MARIADB_REMOVED_OPTION
(commit 1bc9cce7) without breaking
any upgrades.

DICT_ERR_IGNORE_INDEX: Replaces DICT_ERR_IGNORE_INDEX_ROOT and
DICT_ERR_IGNORE_CORRUPT, which were always set equally.

dict_load_indexes(): Report "No indexes found for table" in
a uniform way, and only when the DICT_ERR_IGNORE_INDEX flag is
not set.

If the clustered index is marked corrupted, and the operation
is DICT_ERR_IGNORE_DROP (we are about to drop the table), we will
load the metadata; else, we will return DB_INDEX_CORRUPT.

If SYS_INDEXES.PAGE is FIL_NULL, report an error or warning
unless we are about to drop the table.

dict_load_table_one(): Simplify the logic.