MB-51737 Allow AVOID_ variant as negative optimizer hints

In addition to the NO_ and NO_USE_ version of negative optimizer
hints, we also allow AVOID_ variant as an alias:

AVOID_INDEX:     same as NO_INDEX
AVOID_INDEX_FTS: same as NO_INDEX_FTS
AVOID_NL:        same as NO_USE_NL
AVOID_HASH:      same as NO_USE_HASH

Change-Id: I520326a170d7371f595f3ed6a2a1e7e2fe77400b
Reviewed-on: https://review.couchbase.org/c/query/+/173375
Reviewed-by: Sitaram Vemulapalli <sitaram.vemulapalli@couchbase.com>
Tested-by: Bingjie Miao <bingjie.miao@couchbase.com>