fix: apply initially set custom field value to inputs

[web-padawan]

Description

Fixes #7871

Added logic to store the value property set initially and apply it to inputs after they are populated.

Also added integration tests to cover the case when inputs are not yet upgraded (only happens for Vaadin web components but works with native <input> elements, see the issue description).

Type of change

• Bugfix

[sonarcloud]

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

[vaadin-bot]

Hi @web-padawan and @web-padawan, when i performed cherry-pick to this commit to 24.4, i have encountered the following issue. Can you take a look and pick it manually?
Error Message:
Error: Command failed: git cherry-pick 783abaa
error: could not apply 783abaa... fix: apply initially set custom field value to inputs (#7882)
hint: After resolving the conflicts, mark them with
hint: "git add/rm ", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".