swarm: ctx propagation; bmt fixes; pss generic notification framework (#17150)

* cmd/swarm: minor cli flag text adjustments

* swarm/api/http: sticky footer for swarm landing page using flex

* swarm/api/http: sticky footer for error pages and fix for multiple choices

* cmd/swarm, swarm/storage, swarm: fix  mingw on windows test issues

* cmd/swarm: update description of swarm cmd

* swarm: added network ID test

* cmd/swarm: support for smoke tests on the production swarm cluster

* cmd/swarm/swarm-smoke: simplify cluster logic as per suggestion

* swarm: propagate ctx to internal apis (#754)

* swarm/metrics: collect disk measurements

* swarm/bmt: fix io.Writer interface

  * Write now tolerates arbitrary variable buffers
  * added variable buffer tests
  * Write loop and finalise optimisation
  * refactor / rename
  * add tests for empty input

* swarm/pss: (UPDATE) Generic notifications package (#744)

swarm/pss: Generic package for creating pss notification svcs

* swarm: Adding context to more functions

* swarm/api: change colour of landing page in templates

* swarm/api: change landing page to react to enter keypress

swarm/storage/hasherstore.go

@@ -17,6 +17,7 @@
 package storage
 
 import (
+	"context"
 	"fmt"
 	"sync"
 
@@ -126,9 +127,10 @@ func (h *hasherStore) Close() {
 // Wait returns when
 //    1) the Close() function has been called and
 //    2) all the chunks which has been Put has been stored
-func (h *hasherStore) Wait() {
+func (h *hasherStore) Wait(ctx context.Context) error {
 	<-h.closed
 	h.wg.Wait()
+	return nil
 }
 
 func (h *hasherStore) createHash(chunkData ChunkData) Address {