fix: formkit selector not listening to data after defaulting to first option

[LIlGG]

What type of PR is this?

/kind bug
/area ui
/milestone 2.20.x

What this PR does / why we need it:

当 formkit 选择器初始没有值的情况下，会默认选择第一项，但这同时会导致监听器取消监听，进而无法监听到后续的 value 值变更。

此 PR 将选择值的逻辑与自动选择第一项分开，用于解决此问题。

How to test it?

测试当选择器不存在初始值时，后续通过 v-model 传入的值是否还会使当前选项进行变更。

Does this PR introduce a user-facing change?

解决 FormKit 选择器回显数据异常的问题

[LIlGG]

/cherrypick release-2.19

[halo-dev-bot]

@LIlGG: once the present PR merges, I will cherry-pick it on top of release-2.19 in a new PR and assign it to you.

In response to this:

/cherrypick release-2.19

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.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.05%. Comparing base (6cd8dc8) to head (f3ac14c).
Report is 47 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6571      +/-   ##
============================================
- Coverage     58.18%   58.05%   -0.13%     
- Complexity     3774     3917     +143     
============================================
  Files           651      670      +19     
  Lines         22125    22954     +829     
  Branches       1538     1573      +35     
============================================
+ Hits          12873    13327     +454     
- Misses         8641     9010     +369     
- Partials        611      617       +6     

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[ruibaby]

/lgtm

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ruibaby

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• ui/OWNERS [ruibaby]

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[halo-dev-bot]

@LIlGG: new pull request created: #6574

In response to this:

/cherrypick release-2.19

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.