This PR improves compatibility with specs installed before #45189, and with externals specifying a compiler, by using the annotated compiler to "satisfy" a spec query.
On top of that, the PR adds a new flag for:
```console
$ spack find --specfile-format -I %gcc
-- linux-ubuntu20.04-icelake / gcc@10.5.0 -----------------------
[+] [v4] ca-certificates-mozilla@2023-05-30 [e] [v4] cmake@3.31.6 [+] [v4] gcc-runtime@10.5.0 [e] [v4] glibc@2.31 [+] [v4] gmake@4.4.1 [+] [v4] hdf5@1.14.5 [+] [v4] pkgconf@2.2.0 [+] [v4] zlib-ng@2.2.1
==> 8 installed packages
```
which shows the specfile format of the specs being retrieved.
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