cabal-install executable-stripping is off by default, contrary to documentation

**Describe the bug**
According to https://cabal.readthedocs.io/en/stable/cabal-project-description-file.html#cfg-field-executable-stripping, executable stripping is on by default ("Default value: `True`"). But it isn't.

**To Reproduce**
```
$ mkdir hello-world && cd hello-world
$ cabal init -n
[Info] Guessing dependencies...
[Info] Using cabal specification: 3.12
[Warn] unknown license type, you must put a copy in LICENSE yourself.
[Info] Creating fresh file CHANGELOG.md...
[Info] Creating fresh directory ./app...
[Info] Creating fresh file app/Main.hs...
[Info] Creating fresh file hello-world.cabal...
[Warn] No synopsis given. You should edit the .cabal file and add one.
[Info] You may want to edit the .cabal file and add a Description field.

$ cabal install --install-method=copy --installdir=bin
Wrote tarball sdist to
.../hello-world/dist-newstyle/sdist/hello-world-0.1.0.0.tar.gz
Resolving dependencies...
Build profile: -w ghc-9.2.8 -O1
In order, the following will be built (use -v for more details):
- hello-world-0.1.0.0 (exe:hello-world) (requires build)
Starting hello-world-0.1.0.0 (exe:hello-world)
Building hello-world-0.1.0.0 (exe:hello-world)
Installing hello-world-0.1.0.0 (exe:hello-world)
Completed hello-world-0.1.0.0 (exe:hello-world)
Copying 'hello-world' to 'bin/hello-world'
$ file bin/hello-world
bin/hello-world: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=f01f23649275f7d42dfb4b6875ba1eaab4558218, with debug_info, not stripped
```

NB: **with debug_info, not stripped**

**Expected behavior**
For comparison:
```
$ rm bin/hello-world
$ { echo 'packages: .'; echo 'executable-stripping: True'; } > cabal.project
$ cabal install --install-method=copy --installdir=bin
Wrote tarball sdist to
.../hello-world/dist-newstyle/sdist/hello-world-0.1.0.0.tar.gz
Resolving dependencies...
Build profile: -w ghc-9.2.8 -O1
In order, the following will be built (use -v for more details):
- hello-world-0.1.0.0 (exe:hello-world) (requires build)
Starting hello-world-0.1.0.0 (exe:hello-world)
Building hello-world-0.1.0.0 (exe:hello-world)
Installing hello-world-0.1.0.0 (exe:hello-world)
Completed hello-world-0.1.0.0 (exe:hello-world)
Copying 'hello-world' to 'bin/hello-world'
$ file bin/hello-world
bin/hello-world: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=400106adf4c1724d0afd02e49918c9ea835e8dc9, stripped
```

NB: **stripped**

This is the result I would have expected without setting `executable-stripping` manually in the project file.

**System information**
- Operating system: Ubuntu Linux
- `cabal`, `ghc` versions: 3.12.1.0, 9.2.8

Start with the cabal install path and the executable-stripping configuration described in the issue. Reproduce the Ubuntu case with and without executable-stripping in cabal.project, then verify that the default result matches the documented default and the explicit setting using file.

Written by the indexing model from the issue text.