2.15.4 fixes, enhancements and experimental

Core

• Accept encoded connection urls #674 @scottf
• Only track duplicate responses when advanced tracking is on #659 @scottf

JetStream

• consumer info change to sequence_info from sequence_pair #679 @scottf
• consumer filter subject is now modifiable #676 @scottf
• handle updated account stats #668 @scottf
• Ability to create an External object #661 @scottf

KV

• ability to update bucket config #662 @scottf

Experimental

• expose management getStreamNamesBySubjectFilter #681 @scottf
• experimental pull reader #683 @scottf

Tests

• Add test for NKey.clear #663 @lacinoire

Misc

• remove comments that say durable is required during pull #675 @scottf
• better push queue example #670 @scottf
• fix inactive threshold doc #660 @scottf