test/*.el: Avoid byte-compiler warnings

test/*.el: Avoid byte-compiler warnings

* test/lisp/abbrev-tests.el (abbrev-table-p-test): Remove unused 'let*'.

* test/lisp/faces-tests.el (faces--test): New customization group.
(faces--test1, faces--test2): Use it.

* test/lisp/ffap-tests.el (ffap-tests-25243):
Call 'mark-whole-buffer' interactively.

* test/lisp/ibuffer-tests.el (ibuffer-filter-groups, ibuffer-filtering-alist)
(ibuffer-filtering-qualifiers, ibuffer-save-with-custom)
(ibuffer-saved-filter-groups, ibuffer-saved-filters): Defvar.
(ibuffer-format-qualifier, ibuffer-unary-operand): Declare.

* test/lisp/minibuffer-tests.el (completion-test1):
Mark unused lexical arguments.

* test/lisp/simple-tests.el (simple-test--dummy-buffer): Wrap result in
'with-no-warnings' to avoid them when the macro is invoked for effect.

* test/lisp/emacs-lisp/cl-seq-tests.el (cl-seq-count-test):
Mark unused lexical arguments.

* test/lisp/emacs-lisp/let-alist-tests.el (let-alist-surface-test):
Mark unused lexical arguments.
(let-alist-cons): Remove unused let binding.

* test/lisp/net/dbus-tests.el (dbus-debug): Defvar.
(dbus-get-unique-name): Declare.

* test/lisp/progmodes/python-tests.el (python-bob-infloop-avoid):
Call 'font-lock-fontify-buffer' interactively.

* test/lisp/textmodes/tildify-tests.el (tildify-space-undo-test--test):
Mark unused lexical argument.