When copying files to a container directory, we were running `chown` on
the files using run_chroot, which in addition to using the chroot
command is doing other things like setting up mount points and other
things not needed for running `chown`. Simply using `chroot` should be
enough and faster.

When an input_files is a directory, instead of passing each files
included in the directory individually to remote_put, we just pass the
directory and expect remote_put to copy it recursively.

Since in the case of container, each call to remote_put is a significant
overhead, this makes it much faster when including a directory
containing many files.

Default value for compress_tar was changed in
a91d4653.

Instead we expect the argument to follow on the same line.

This includes:

compress_tar
buildconf: num_procs (which is now just num_procs)
ENV
gpg_wrapper
var: touch (which is now just touch)

Closes: #40040.

In templates, the `p` variable allowed to access the current project's
rbm config. With the support for projects in modules, it would need to
be adapted. However we never used this variable in tor-browser-build,
and it is not very useful (it's usually better to use c() to access
config), so we remove it.

We also remove the `gpg_keyring_dir` option since this would make things
more complex, and changing the `keyring` directory name is not very
useful.

Makes it much easier to find the source of the error.

We incorrectly parsed /etc/subgid, assuming that the first field is the
gid of the user. However it is the uid.

When using remote_exec, we collect input_files in a temporary directory,
before copying them to the "remote" (for example a container). As we
don't normally modify the files inside this temporary directory, it is
safe to use hard link rather than copies of the files.

When remote_exec is not used, we don't use hard links by default, but
link_input_files can be set to 1 to use hard links.

rbm_tmp_dir is a directory inside tmp_dir that is automatically removed
when rbm exits.

We also fix an issue in urlget when used within the exec script of an
input file. In this case the input_files_id was depending on the value
of tmp_dir because it is used in urlget. We fix that be setting
getting_input_files_id when computing input_files ids, so that urlget
can avoid using tmp_dir in this case.

For simplification, we remove some unused features. Those features can
still be reimplemented externally if needed.

For example, the "rbm rpm" command can be replaced with
"rbm build --step rpm" and a definition of an rpm step in rbm.conf.

We remove the following options:
 - version_command
 - rpm
 - rpmbuild
 - srpm
 - rpmspec
 - rpm_rel
 - debian_create
 - deb
 - deb_src
 - use_pbuilder
 - debian_revision

And the following commands:
 - rpmspec
 - rpm
 - srpm
 - deb-src
 - deb
 - pkg
 - publish