"func extension install" command does not create extensions.json at bin directory

"func extension install" command create `extensions.json` under `bin/bin` directory but not in `bin` directory.
Functions Host does not load extensions when it started with `func start` command. We need manually copy extensions.json from `bin/bin` to `bin` to load it. Is this expected behavior?


extensions.csproj
```

net6.0
v4











PreserveNewest


PreserveNewest
Never

```

```
$ func extensions install
Microsoft (R) Build Engine version 17.1.1+a02f73656 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

Determining projects to restore...
All projects are up-to-date for restore.
SampleWebJobExtension -> /mnt/c/Users/toshida.FAREAST/source/repos/SampleWebJobExtension/jsFunc/bin/SampleWebJobExtension.dll
extensions -> /mnt/c/Users/toshida.FAREAST/source/repos/SampleWebJobExtension/jsFunc/bin/extensions.dll

Build succeeded.
0 Warning(s)
0 Error(s)

Time Elapsed 00:00:15.91
```

Start with the provided extensions.csproj and reproduce `func extensions install`, checking where extensions.json is written relative to the bin directory. Then run `func start` and verify that the Functions Host loads the extensions without manually copying the file; the completed fix should make the generated metadata available in the expected bin location.

Written by the indexing model from the issue text.