ADD userguide/managingApp/rolling-back-a-deployment

[rahulshendre]

What this PR does:

File by file commit from the bigger PR - #6345

Adds the “Rolling back a deployment” page under User Guide → Managing Application.

Related to #6395

Why we need it:

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[eeshaanSA]

PTAL and review my work, @rahulshendre . Let me know if I missed something. 👀

[eeshaanSA]

This page is closely related to this.

Plan this page accordingly. Technically, this page should be a brief of rollback, and then guide the user to Rolling Back a deployment page.

[rahulshendre]

@eeshaanSA, I have added a reference to this in the page.
PTAL and let me know if any changes are needed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.63%. Comparing base (ebc267c) to head (8e74c66).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #6410       +/-   ##
===========================================
+ Coverage   28.87%   67.63%   +38.75%     
===========================================
  Files         560       25      -535     
  Lines       59955     2283    -57672     
===========================================
- Hits        17313     1544    -15769     
+ Misses      41321      651    -40670     
+ Partials     1321       88     -1233     

Flag	Coverage Δ
.	?
.-pkg-app-pipedv1-plugin-analysis	?
.-pkg-app-pipedv1-plugin-kubernetes	?
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	67.63% <ø> (ø)
.-pkg-app-pipedv1-plugin-scriptrun	?
.-pkg-app-pipedv1-plugin-terraform	?
.-pkg-app-pipedv1-plugin-wait	?
.-pkg-app-pipedv1-plugin-waitapproval	?
.-pkg-plugin-sdk	?
.-tool-actions-gh-release	?
.-tool-actions-plan-preview	?
.-tool-codegen-protoc-gen-auth	?

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