Fix the problem that theme assets could not be found after the first initialization

[JohnNiang]

What type of PR is this?

/kind bug
/area core
/milestone 2.17.x

What this PR does / why we need it:

When initialized for the first time, the folder ${halo.work-dir}/themes does not exist, resulting in the themes path being ignored when invoking themeRootResource.createRelative(themeName + "/templates/assets/");. It works very well after restarting.

This PR fixes the problem by resolving theme resource directly rather than delegating to PathResourceResolver.

Which issue(s) this PR fixes:

Fixes #6048

Does this PR introduce a user-facing change?

修复首次初始化后无法正常访问主题资源的问题

[JohnNiang]

/cherrypick release-2.16

[halo-dev-bot]

@JohnNiang: once the present PR merges, I will cherry-pick it on top of release-2.16 in a new PR and assign it to you.

In response to this:

/cherrypick release-2.16

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.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.2% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 28.57143% with 5 lines in your changes missing coverage. Please review.

Project coverage is 56.47%. Comparing base (5fdf6c0) to head (2275dad).
Report is 230 commits behind head on main.

Files	Patch %	Lines
.../halo/app/theme/config/ThemeWebFluxConfigurer.java	28.57%	5 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6049      +/-   ##
============================================
- Coverage     56.91%   56.47%   -0.44%     
- Complexity     3319     3541     +222     
============================================
  Files           587      622      +35     
  Lines         18968    20957    +1989     
  Branches       1401     1478      +77     
============================================
+ Hits          10795    11836    +1041     
- Misses         7594     8521     +927     
- Partials        579      600      +21     

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[ruibaby]

/lgtm

[ruibaby]

/lgtm

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ruibaby

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• OWNERS [ruibaby]

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[halo-dev-bot]

@JohnNiang: new pull request created: #6050

In response to this:

/cherrypick release-2.16

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.