rest-api: Fix POST error for /api/sys/server and /api/sys/psu_update

[louis-nexthop]

Description

Fixes #272

1. Fix POST handler error: replace get_data_from_generator(request.json()) with parsed ctx.json_data since aiohttp >= 3.0.0 no longer returns generator-based couroutine.
2. Add RequestContext dataclass: thread-safe snapshot of RestAPI request payload, captured before entering the executor thread.
3. Add @async_web_handler_in_common_executor decorator for request handlers; builds RequestContext on the event loop and feeds it to the handlers.
4. Migrate all common_endpoint.py handlers to (self, ctx: RequestContext) and use @async_web_handler_in_common_executor.
5. Rename @common_force_async → @async_in_common_executor for non-request functions.
6. Extract _run_in_common_executor() helper; unify on get_running_loop().

Motivation

Calling POST action with JSON data would fail with TypeError("'coroutine' object is not an iterator"):

root@bmc-oob:~# curl -s -X POST \
  -H "Content-Type: application/json" \
  -d "{\"action\":\"power-on\"}" \
  http://localhost:8080/api/sys/server
{"Information": {"reason": "TypeError(\"'coroutine' object is not an iterator\")"}, "Actions": [], "Resources": []}

This is because of the transition from aiohttp 2.3.10 -> aiohttp 3.0.0, where Request.json() no longer returns a generator-based coroutine (v2.3.10 vs v3.0.0).

However, /api/sys/server and /api/sys/psu_update endpoints still rely on get_data_from_generator(request.json()) which assumes a generator-based coroutine. So, instead, we should use await request.json() to get the data.

Caveat:

• rocko and dunfell still use aiohttp 2.1.0, as shown here (aiohttp_2.1.0.bb).
• kirkstone and master uses python3-aiohttp from meta-openembedded. As of now:

Yocto branch	Pinned commit (yocto_repos.sh)	aiohttp	evidence
lf-kirkstone	91c406079	3.8.1	python3-aiohttp_3.8.1.bb
lf-master	ea1e8642b	3.13.5	python3-aiohttp_3.13.5.bb

• await request.json() should also work on aiohttp 2.1.0 (confirmed with local testing, using python 3.8 + aiohttp 2.1.0)
• request.can_read_body() does not exist in aiohttp 2.1.0, so it is handled separately

Test Plan

Before:

root@bmc-oob:~# python3 -c "import aiohttp; print(aiohttp.__version__)"
3.13.5
root@bmc-oob:~# curl -s -X POST \
  -H "Content-Type: application/json" \
  -d "{\"action\":\"power-on\"}" \
  http://localhost:8080/api/sys/server
{"Information": {"reason": "TypeError(\"'coroutine' object is not an iterator\")"}, "Actions": [], "Resources": []}

After:

root@bmc-oob:~# python3 -c "import aiohttp; print(aiohttp.__version__)"
3.13.5
root@bmc-oob:~# curl -s -X POST \
  -H "Content-Type: application/json" \
  -d "{\"action\":\"power-on\"}" \
  http://localhost:8080/api/sys/server
{"result": "failure", "reason": "already on"}

• /redfish/v1/Chassis/1/Sensors which has dependency on @async_in_common_executor still work:

root@bmc-oob:~# curl http://localhost:8080/redfish/v1/Chassis/1/Sensors
{"@odata.type": "#SensorCollection.SensorCollection", "Name": "Chassis sensors", "Members@odata.count": 0, "Members": [], "@odata.id": "/redfish/v1/Chassis/1/Sensors"}

[meta-codesync]

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