feat: implement Flow hotswap API

[mcollovati]

Implements Flow hotswap API and removes the hotswap agent plugin.

Part of vaadin/flow#19261

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.81%. Comparing base (c4dc4c2) to head (b4e14f7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2590 +/- ## ======================================= Coverage 90.81% 90.81% ======================================= Files 66 66 Lines 2765 2765 Branches 528 528 ======================================= Hits 2511 2511 Misses 79 79 Partials 175 175 ``` | [Flag](https://app.codecov.io/gh/vaadin/hilla/pull/2590/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vaadin) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/vaadin/hilla/pull/2590/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vaadin) | `90.81% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vaadin#carryforward-flags-in-the-pull-request-comment) to find out more.

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[sonarcloud[bot]]

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