[9.18] Properly name ADB hashmap memory context

The ADB hashmaps are stored in extra memory contexts, so the hash tables are excluded from the overmem accounting. The new memory context was unnamed, give it a proper name.

Same thing has happened with extra memory context used for named global log context - give the extra memory context a proper name.

(cherry picked from commit 3cda9f9f)

Closes #3806 (closed)

Backport of MR !7447 (merged)