chore: replace deprecated PingCAP download domains

[wuhuizuo]

Summary

• replace deprecated download.pingcap.org references with download.pingcap.com
• replace deprecated charts.pingcap.org references with charts.pingcap.com where present
• keep the existing paths and protocols unchanged

Validation

• git diff --check
• verified no remaining download.pingcap.org / charts.pingcap.org references in the patched branch

[ti-chi-bot]

Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

Details

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign gmhdbjd for approval. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

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Details

Needs approval from an approver in each of these files:

• OWNERS
• dm/OWNERS

Approvers can indicate their approval by writing /approve in a comment
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[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

1. It must be LGTMed and approved by the reviewers firstly.
2. For pull requests to TiDB-x branches, it must have no failed tests.
3. AFTER it has lgtm and approved labels, please wait for the cherry-pick merging approval from triage owners.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[gemini-code-assist]

Code Review

This pull request updates various download URLs across documentation and scripts from 'download.pingcap.org' to 'download.pingcap.com'. The reviewer suggested updating an insecure 'http' URL to 'https' in 'dm/tests/download-compatibility-test-binaries.sh' to ensure secure transport and consistency.

[gemini-code-assist]

Use https instead of http for downloading binaries to ensure a secure connection and maintain consistency with other download URLs in the project. This helps prevent potential man-in-the-middle attacks during the download process.

Suggested change

	"http://download.pingcap.com/tidb-enterprise-tools-latest-linux-amd64.tar.gz"
	"https://download.pingcap.com/tidb-enterprise-tools-latest-linux-amd64.tar.gz"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (release-8.5@d6d53ad). Learn more about missing BASE report.

Additional details and impacted files

Components	Coverage Δ
cdc	57.5620% <0.0000%> (?)
dm	48.9160% <0.0000%> (?)
engine	50.7388% <0.0000%> (?)

Flag	Coverage Δ
cdc	57.5620% <ø> (?)
unit	53.3830% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

@@               Coverage Diff                @@
##             release-8.5     #12583   +/-   ##
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  Coverage               ?   53.3830%           
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  Files                  ?       1026           
  Lines                  ?     137836           
  Branches               ?          0           
================================================
  Hits                   ?      73581           
  Misses                 ?      58750           
  Partials               ?       5505           

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