docs: add design doc for ebs br support to multiple k8s clusters

[BornChanger]

What problem does this PR solve?

What is changed and how does it work?

Code changes

• Has Go code change
• Has CI related scripts change

Tests

• Unit test
• E2E test
• Manual test
• No code

Side effects

• Breaking backward compatibility
• Other side effects:

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release Notes

Please refer to Release Notes Language Style Guide before writing the release note.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has not been approved.

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[BornChanger]

/cc @WangLe1321 @grovecai

[BornChanger]

/retest

[codecov-commenter]

Codecov Report

Merging #5004 (111e006) into master (3058685) will decrease coverage by 0.04%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5004      +/-   ##
==========================================
- Coverage   57.30%   57.26%   -0.04%     
==========================================
  Files         243      243              
  Lines       27298    27308      +10     
==========================================
- Hits        15642    15637       -5     
- Misses      10135    10148      +13     
- Partials     1521     1523       +2     

Flag	Coverage Δ
unittest	57.26% <ø> (-0.04%)	⬇️

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: csuzhangxc, WangLe1321

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 [WangLe1321,csuzhangxc]

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

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-25 09:12:56.67781958 +0000 UTC m=+1486341.226835568: ☑️ agreed by csuzhangxc.
• 2023-08-25 09:15:21.160404927 +0000 UTC m=+1486485.709420934: ✖️🔁 reset by ti-chi-bot[bot].
• 2023-08-25 09:59:28.199274398 +0000 UTC m=+1489132.748290385: ☑️ agreed by WangLe1321.

[csuzhangxc]

/cherry-pick release-1.5

[ti-chi-bot]

@csuzhangxc: The label(s) /release-1.5 cannot be applied, because the repository doesn't have them.

In response to this:

/cherry-pick release-1.5

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 ti-community-infra/tichi repository.

[ti-chi-bot]

@csuzhangxc: new pull request created to branch release-1.5: #5270.

In response to this:

/cherry-pick release-1.5

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 ti-community-infra/tichi repository.