Fix the problem that plugins without jar file may not be deleted

[JohnNiang]

What type of PR is this?

/kind bug
/area core
/area plugin
/milestone 2.18.x

What this PR does / why we need it:

This PR checks if the plugin is already unloaded while getting dependents to fix the problem that plugins without jar file may not be deleted or not be enabled or disabled.

Which issue(s) this PR fixes:

Fixes #6072

Special notes for your reviewer:

1. Try to move plugins folder to another folder
2. Restart Halo
3. Try to change state of plugins or delete plugins directly
4. See the result

Does this PR introduce a user-facing change?

修复在没有插件文件的情况下可能无法删除插件的问题

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Project coverage is 58.27%. Comparing base (bc10336) to head (efacd5c).
Report is 82 commits behind head on main.

Files	Patch %	Lines
...in/java/run/halo/app/plugin/HaloPluginManager.java	90.90%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6334      +/-   ##
============================================
+ Coverage     54.51%   58.27%   +3.76%     
- Complexity     3523     3763     +240     
============================================
  Files           646      646              
  Lines         21862    21979     +117     
  Branches       1528     1545      +17     
============================================
+ Hits          11917    12809     +892     
+ Misses         9328     8550     -778     
- Partials        617      620       +3     

☔ View full report in Codecov by Sentry.
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[JohnNiang]

/cherrypick release-2.17

[halo-dev-bot]

@JohnNiang: once the present PR merges, I will cherry-pick it on top of release-2.17 in a new PR and assign it to you.

In response to this:

/cherrypick release-2.17

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/test-infra repository.

[guqing]

/lgtm

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: guqing

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• OWNERS [guqing]

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[halo-dev-bot]

@JohnNiang: #6334 failed to apply on top of branch "release-2.17":

Applying: Fix the problem that plugin may not be deleted while its jar file deleted
Using index info to reconstruct a base tree...
M	application/src/main/java/run/halo/app/plugin/HaloPluginManager.java
Falling back to patching base and 3-way merge...
Auto-merging application/src/main/java/run/halo/app/plugin/HaloPluginManager.java
CONFLICT (content): Merge conflict in application/src/main/java/run/halo/app/plugin/HaloPluginManager.java
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fix the problem that plugin may not be deleted while its jar file deleted
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherrypick release-2.17

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/test-infra repository.