Slim ServerMiddleware to `(ctx, call_next)` and add `OpenTelemetryMiddleware` #2896

Job	Run time
checks / pre-commit	40s
checks / readme-snippets	11s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 4s
checks / test (3.10, locked, ubuntu-latest)	1m 5s
checks / test (3.10, locked, windows-latest)	1m 36s
checks / test (3.11, locked, ubuntu-latest)	56s
checks / test (3.11, lowest-direct, windows-latest)	1m 35s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 4s
checks / test (3.10, lowest-direct, windows-latest)	1m 30s
checks / test (3.12, lowest-direct, windows-latest)	1m 31s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 6s
checks / test (3.11, locked, windows-latest)	1m 22s
checks / test (3.12, locked, ubuntu-latest)	1m 6s
checks / test (3.14, lowest-direct, windows-latest)	1m 27s
checks / test (3.13, locked, windows-latest)	1m 32s
checks / test (3.14, locked, windows-latest)	2m 18s
checks / test (3.12, locked, windows-latest)	1m 27s
checks / test (3.13, lowest-direct, windows-latest)	1m 28s
checks / test (3.14, lowest-direct, ubuntu-latest)	56s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 1s
checks / test (3.14, locked, ubuntu-latest)	1m 57s
checks / test (3.13, locked, ubuntu-latest)	55s
all-green	5s
	27m 52s

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