Parser.Dep: emitting a small header in the .depend

[mtzguido]

Example:

$ cat ulib/.depend | head
# This .depend was generated by F* 2024.09.05~dev
# Executable: "/home/guido/r/fstar/master/bin/fstar.exe"
# Hash: 1fd56a7d4ada8d7e5879ec07539b06e6cd5f287b-dirty
# Running in directory "/home/guido/r/fstar/master/ulib"
# Command line arguments: "["../bin/fstar.exe", "--warn_error", "@271-330@247", "--ext", "context_pruning", "--use_hints", "--cache_dir", ".cache", "--hint_dir", ".hints", "--silent", "--cache_checked_modules", "--odir", "_output", "@.depend.rsp", "--output_deps_to", ".depend"]"

.cache/FStar.Seq.Equiv.fsti.checked: FStar.Seq.Equiv.fsti\
        .cache/FStar.IntegerIntervals.fst.checked\
        .cache/FStar.Seq.Properties.fsti.checked\
        .cache/FStar.Seq.Base.fsti.checked\