front: using config stored in db for stdcm v2

[sim51]

Fix #8239

To test it, you need to insert a row in the table stdcm_search_environment

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 2.43902% with 200 lines in your changes missing coverage. Please review.

Project coverage is 37.49%. Comparing base (39e7b9d) to head (b1d22a4).

Files	Patch %	Lines
...ont/src/applications/stdcmV2/hooks/useStdcmEnv.tsx	0.00%	49 Missing and 1 partial :warning:
...ont/src/applications/stdcmV2/views/StdcmViewV2.tsx	0.00%	35 Missing :warning:
.../src/applications/stdcm/utils/formatStdcmConfV2.ts	0.00%	27 Missing :warning:
...rc/applications/stdcmV2/components/StdcmOrigin.tsx	0.00%	26 Missing and 1 partial :warning:
...tions/stdcmV2/components/StdcmEmptyConfigError.tsx	0.00%	20 Missing and 1 partial :warning:
front/src/reducers/osrdconf/stdcmConf/index.ts	5.26%	18 Missing :warning:
editoast/src/views/v2/timetable/stdcm.rs	0.00%	15 Missing :warning:
...rc/applications/stdcmV2/components/StdcmHeader.tsx	0.00%	6 Missing :warning:
.../src/reducers/osrdconf/osrdConfCommon/selectors.ts	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #8336 +/- ## ============================================ + Coverage 37.07% 37.49% +0.41% Complexity 2165 2165 ============================================ Files 1265 1253 -12 Lines 117058 115653 -1405 Branches 3137 3139 +2 ============================================ - Hits 43404 43366 -38 + Misses 71814 70445 -1369 - Partials 1840 1842 +2 ``` | [Flag](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [core](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `74.94% <ø> (ø)` | | | [editoast](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `66.38% <0.00%> (-0.04%)` | :arrow_down: | | [front](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `15.77% <1.59%> (-0.03%)` | :arrow_down: | | [gateway](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `?` | | | [osrdyne](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `2.71% <ø> (ø)` | | | [railjson_generator](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `87.49% <ø> (ø)` | | | [tests](https://app.codecov.io/gh/OpenRailAssociation/osrd/pull/8336/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `73.00% <100.00%> (+0.02%)` | :arrow_up: | 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=None#carryforward-flags-in-the-pull-request-comment) to find out more.

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[sim51]

I squashed my commits