build caches: collect files to relocate while tarballing w/o file (#48212)

A few changes to tarball creation (for build caches):
- do not run file to distinguish binary from text
- file is slow, even when running it in a batched fashion -- it usually reads all bytes and has slow logic to categorize specific types
- we don't need a highly detailed file categorization; a crude categorization of elf, mach-o, text suffices.
detecting elf and mach-o is straightforward and cheap
- detecting utf-8 (and with that ascii) is highly accurate: false positive rate decays exponentially as file size increases. Further it's not only the most common encoding, but the most common file type in package prefixes.
iso-8859-1 is cheaply (but heuristically) detected too, and sufficiently accurate after binaries and utf-8 files are classified earlier
- remove file as a dependency of Spack in general, which makes Spack itself easier to install
- detect file type and need to relocate as part of creating the tarball, which is more cache friendly and thus faster

.github/workflows/bootstrap.yml

@@ -161,11 +161,7 @@ jobs:
           source share/spack/setup-env.sh
           spack -d gpg list
           tree $HOME/.spack/bootstrap/store/
-      - name: Bootstrap File
-        run: |
-          source share/spack/setup-env.sh
-          spack -d python share/spack/qa/bootstrap-file.py
-          tree $HOME/.spack/bootstrap/store/
+
 
   windows:
     runs-on: "windows-latest"
@@ -196,9 +192,3 @@ jobs:
           spack -d gpg list
           ./share/spack/qa/validate_last_exit.ps1
           tree $env:userprofile/.spack/bootstrap/store/
-      - name: Bootstrap File
-        run: |
-          ./share/spack/setup-env.ps1
-          spack -d python share/spack/qa/bootstrap-file.py
-          ./share/spack/qa/validate_last_exit.ps1
-          tree $env:userprofile/.spack/bootstrap/store/