bump alpine to 3.18.5 to address CVE concerns

[zhzhuang-zju]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
bump alpine to 3.18.5 to address CVE-2023-5363
Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

➜  karmada git:(master) ✗ trivy image --format table  docker.io/karmada/karmada-operator:new 
2023-12-06T10:42:09.997+0800    INFO    Need to update DB
2023-12-06T10:42:09.997+0800    INFO    DB Repository: ghcr.io/aquasecurity/trivy-db
2023-12-06T10:42:09.997+0800    INFO    Downloading DB...
41.17 MiB / 41.17 MiB [-----------------------------------------------------------------------------------------------------------------------------------------------------------------------] 100.00% 1.89 MiB p/s 22s
2023-12-06T10:42:33.531+0800    INFO    Vulnerability scanning is enabled
2023-12-06T10:42:33.531+0800    INFO    Secret scanning is enabled
2023-12-06T10:42:33.531+0800    INFO    If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2023-12-06T10:42:33.531+0800    INFO    Please see also https://aquasecurity.github.io/trivy/v0.45/docs/scanner/secret/#recommendation for faster secret detection
2023-12-06T10:42:36.627+0800    INFO    Detected OS: alpine
2023-12-06T10:42:36.627+0800    INFO    Detecting Alpine vulnerabilities...
2023-12-06T10:42:36.629+0800    INFO    Number of language-specific files: 1
2023-12-06T10:42:36.629+0800    INFO    Detecting gobinary vulnerabilities...

docker.io/karmada/karmada-operator:new (alpine 3.18.5)

Total: 0 (UNKNOWN: 0, LOW: 0, MEDIUM: 0, HIGH: 0, CRITICAL: 0)

Does this PR introduce a user-facing change?:

The base image `alpine` now has been promoted from `alpine:3.18.3` to `alpine:3.18.5`

[RainbowMango]

There are two more places we might need to update as well:

1. karmada/pkg/karmadactl/cmdinit/kubernetes/deploy.go

   Line 117 in 5e3f34c

   DefaultInitImage = "docker.io/alpine:3.15.1"

2. karmada/pkg/karmadactl/cmdinit/kubernetes/deploy.go

   Line 668 in 5e3f34c

   return i.ImageRegistry + "/alpine:3.15.1"

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6128367) 51.80% compared to head (d4bc240) 51.86%.
Report is 34 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4376      +/-   ##
==========================================
+ Coverage   51.80%   51.86%   +0.05%     
==========================================
  Files         243      243              
  Lines       24112    24114       +2     
==========================================
+ Hits        12491    12506      +15     
+ Misses      10941    10925      -16     
- Partials      680      683       +3     

Flag	Coverage Δ
unittests	51.86% <100.00%> (+0.05%)	⬆️

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[zhzhuang-zju]

There are two more places we might need to update as well:

1. karmada/pkg/karmadactl/cmdinit/kubernetes/deploy.go

   Line 117 in 5e3f34c

   DefaultInitImage = "docker.io/alpine:3.15.1"

2. karmada/pkg/karmadactl/cmdinit/kubernetes/deploy.go

   Line 668 in 5e3f34c

   return i.ImageRegistry + "/alpine:3.15.1"

There are two more places we might need to update as well:

1. karmada/pkg/karmadactl/cmdinit/kubernetes/deploy.go

   Line 117 in 5e3f34c

   DefaultInitImage = "docker.io/alpine:3.15.1"

2. karmada/pkg/karmadactl/cmdinit/kubernetes/deploy.go

   Line 668 in 5e3f34c

   return i.ImageRegistry + "/alpine:3.15.1"

done~

[RainbowMango]

/lgtm
/approve

Please help to cherry-pick it to release branches:

• release-1.8
• release-1.7
• release-1.6
• release-1.5

PS:
For the release-1.5, we might need to release a final patch release.

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [RainbowMango]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[zhzhuang-zju]

/lgtm /approve

Please help to cherry-pick it to release branches:

• release-1.8
• release-1.7
• release-1.6
• release-1.5

PS: For the release-1.5, we might need to release a final patch release.

/assign