Show update check message to users once in 24 hours

[tejal29]

Relates to #5711

Update check prompts are shown on every command run.
This could annoy the users and get them to switch off update checks.

In this PR

1. Add a config section update with last-prompted field.
2. Add logic to display update check prompt only once in 24 hours.

This does not change the existing update check behavior. See #5741 for that.

Testing done:

1. Build a binary with latest version & make sure
   a) update check message is not shown.
   b) update-config is not updated with last-prompted

GOOS=darwin GOARCH=amd64 CGO_ENABLED=1 \
go build -gcflags="all=-N -l" -tags "release " -ldflags "-X github.com/GoogleContainerTools/skaffold/pkg/skaffold/version.version=v1.24.0 -s -w " -o out/skaffold github.com/GoogleContainerTools/skaffold/cmd/skaffold

.➜  multi-config-microservices git:(show_update_check_dailu) ✗ ../../out/skaffold build -d gcr.io/tejal-gke1
Generating tags...
 - base -> gcr.io/tejal-gke1/base:v1.23.0-36-gbf79f0788
 - leeroy-app -> gcr.io/tejal-gke1/leeroy-app:v1.23.0-36-gbf79f0788
 - leeroy-web -> gcr.io/tejal-gke1/leeroy-web:v1.23.0-36-gbf79f0788
Checking cache...
 - base: Found Remotely
 - leeroy-app: Found Remotely
 - leeroy-web: Found Remotely                  

➜  multi-config-microservices git:(show_update_check_dailu) ✗ cat ~/.skaffold/config
global:
  survey:
    last-prompted: "2021-04-27T13:32:59-07:00"
  collect-metrics: true
kubeContexts: []

2. Build a binary with older version & make sure
   a) update message is shown

➜ GOOS=darwin GOARCH=amd64 CGO_ENABLED=1 \
 go build -gcflags="all=-N -l" -tags "release " -ldflags "-X github.com/GoogleContainerTools/skaffold/pkg/skaffold/version.version=v1.22.0 -s -w " -o out/skaffold github.com/GoogleContainerTools/skaffold/cmd/skaffold

➜ ../../out/skaffold build -d gcr.io/tejal-gke1
Generating tags...
 - base -> gcr.io/tejal-gke1/base:v1.23.0-36-gbf79f0788
 - leeroy-app -> gcr.io/tejal-gke1/leeroy-app:v1.23.0-36-gbf79f0788
 - leeroy-web -> gcr.io/tejal-gke1/leeroy-web:v1.23.0-36-gbf79f0788
Checking cache...
 - base: Found Remotely
 - leeroy-app: Found Remotely
 - leeroy-web: Found Remotely
There is a new version (1.23.0) of Skaffold available. Download it from:
  https://github.com/GoogleContainerTools/skaffold/releases/tag/v1.23.0

b) update-config is updated with last-prompted

➜ cat ~/.skaffold/config                       
global:
  survey:
    last-prompted: "2021-04-27T13:32:59-07:00"
  collect-metrics: true
  update-config:
    last-prompted: "2021-05-06T00:14:50-07:00"
kubeContexts: []

c) subsequent invocations don't display the update check messages.

➜  ../../out/skaffold version && ../../out/skaffold build -d gcr.io/tejal-gke1 
v1.22.0

Generating tags...
 - base -> gcr.io/tejal-gke1/base:v1.23.0-36-gbf79f0788
 - leeroy-app -> gcr.io/tejal-gke1/leeroy-app:v1.23.0-36-gbf79f0788
 - leeroy-web -> gcr.io/tejal-gke1/leeroy-web:v1.23.0-36-gbf79f0788
Checking cache...
 - base: Found Remotely
 - leeroy-app: Found Remotely
 - leeroy-web: Found Remotely

d) Change the date to yesterday and make sure update message is displayed

global:
  survey:
    last-prompted: "2021-04-27T13:32:59-07:00"
  collect-metrics: true
  update-config:
    last-prompted: "2021-05-05T00:14:50-07:00".   ## yesterday
kubeContexts: []

➜   ../../out/skaffold build -d gcr.io/tejal-gke1 
Generating tags...
 - base -> gcr.io/tejal-gke1/base:v1.23.0-36-gbf79f0788
 - leeroy-app -> gcr.io/tejal-gke1/leeroy-app:v1.23.0-36-gbf79f0788
 - leeroy-web -> gcr.io/tejal-gke1/leeroy-web:v1.23.0-36-gbf79f0788
Checking cache...
 - base: Found Remotely
 - leeroy-app: Found Remotely
 - leeroy-web: Found Remotely
There is a new version (1.23.0) of Skaffold available. Download it from:
  https://github.com/GoogleContainerTools/skaffold/releases/tag/v1.23.0

[codecov]

Codecov Report

Merging #5795 (210cd8b) into master (ce34201) will decrease coverage by 0.01%.
The diff coverage is 71.42%.

@@            Coverage Diff             @@
##           master    #5795      +/-   ##
==========================================
- Coverage   70.95%   70.93%   -0.02%     
==========================================
  Files         439      438       -1     
  Lines       16408    16434      +26     
==========================================
+ Hits        11642    11658      +16     
- Misses       3913     3920       +7     
- Partials      853      856       +3     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/cmd.go	63.03% <0.00%> (-0.78%)	⬇️
pkg/skaffold/config/util.go	65.85% <70.00%> (+0.44%)	⬆️
pkg/skaffold/update/update.go	48.38% <100.00%> (ø)
cmd/skaffold/app/cmd/runner.go	58.49% <0.00%> (ø)
pkg/skaffold/runner/v2/runner.go	0.00% <0.00%> (ø)
pkg/skaffold/runner/cleanup.go
pkg/skaffold/runner/apply.go
pkg/skaffold/runner/portforwarder.go
pkg/skaffold/runner/runner.go
pkg/skaffold/runner/tester.go
... and 25 more

---

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[MarlonGamez]

will do some manual testing and get back 👍🏼

[MarlonGamez]

lgtm! just a couple nits/q's

[MarlonGamez]

lgtm 👍🏼