`spack spec` output has looked like this for a while:
```console
> spack spec /v5fn6xo /wd2p2v7
Input spec
--------------------------------
- /v5fn6xo
Concretized
--------------------------------
[+] openssl@3.3.1%apple-clang@16.0.0~docs+shared build_system=generic certs=mozilla arch=darwin-sequoia-m1
[+] ^ca-certificates-mozilla@2023-05-30%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
...
Input spec
--------------------------------
- /wd2p2v7
Concretized
--------------------------------
[+] py-six@1.16.0%apple-clang@16.0.0 build_system=python_pip arch=darwin-sequoia-m1
[+] ^py-pip@23.1.2%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
```
But the input spec is right there on the CLI, and it doesn't add anything to the output.
Also, since #44843, specs concretized in the CLI line can be unified, so it makes sense
to display them as we did in #44489 -- as one multi-root tree instead of as multiple
single-root trees.
With this PR, concretize output now looks like this:
```console
> spack spec /v5fn6xo /wd2p2v7
[+] openssl@3.3.1%apple-clang@16.0.0~docs+shared build_system=generic certs=mozilla arch=darwin-sequoia-m1
[+] ^ca-certificates-mozilla@2023-05-30%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
[+] ^gmake@4.4.1%apple-clang@16.0.0~guile build_system=generic arch=darwin-sequoia-m1
[+] ^perl@5.40.0%apple-clang@16.0.0+cpanm+opcode+open+shared+threads build_system=generic arch=darwin-sequoia-m1
[+] ^berkeley-db@18.1.40%apple-clang@16.0.0+cxx~docs+stl build_system=autotools patches=26090f4,b231fcc arch=darwin-sequoia-m1
[+] ^bzip2@1.0.8%apple-clang@16.0.0~debug~pic+shared build_system=generic arch=darwin-sequoia-m1
[+] ^diffutils@3.10%apple-clang@16.0.0 build_system=autotools arch=darwin-sequoia-m1
[+] ^libiconv@1.17%apple-clang@16.0.0 build_system=autotools libs=shared,static arch=darwin-sequoia-m1
[+] ^gdbm@1.23%apple-clang@16.0.0 build_system=autotools arch=darwin-sequoia-m1
[+] ^readline@8.2%apple-clang@16.0.0 build_system=autotools patches=bbf97f1 arch=darwin-sequoia-m1
[+] ^ncurses@6.5%apple-clang@16.0.0~symlinks+termlib abi=none build_system=autotools patches=7a351bc arch=darwin-sequoia-m1
[+] ^pkgconf@2.2.0%apple-clang@16.0.0 build_system=autotools arch=darwin-sequoia-m1
[+] ^zlib-ng@2.2.1%apple-clang@16.0.0+compat+new_strategies+opt+pic+shared build_system=autotools arch=darwin-sequoia-m1
[+] ^gnuconfig@2022-09-17%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
[+] py-six@1.16.0%apple-clang@16.0.0 build_system=python_pip arch=darwin-sequoia-m1
[+] ^py-pip@23.1.2%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
[+] ^py-setuptools@69.2.0%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
[-] ^py-wheel@0.41.2%apple-clang@16.0.0 build_system=generic arch=darwin-sequoia-m1
...
```
With no input spec displayed -- just the concretization output shown as one consolidated
tree and multiple roots.
- [x] remove "Input Spec" section and "Concretized" header from `spack spec` output
- [x] print concretized specs as one BFS tree instead of multiple
---------
Signed-off-by: Todd Gamblin <tgamblin@llnl.gov>
Co-authored-by: Harmen Stoppels <harmenstoppels@gmail.com>
6f948eb847