Make 'eval' use lexical scoping in most tests

Make 'eval' use lexical scoping in most tests

* test/lisp/electric-tests.el (electric-pair-define-test-form)
(define-electric-pair-test):
* test/lisp/emacs-lisp/backtrace-tests.el
(backtrace-tests--uncompiled-functions):
* test/lisp/emacs-lisp/cl-macs-tests.el
(cl-macs-test--symbol-macrolet):
* test/lisp/emacs-lisp/let-alist-tests.el
(let-alist-list-to-sexp):
* test/lisp/emacs-lisp/lisp-tests.el
(elisp-tests-with-temp-buffer, core-elisp-tests-3-backquote):
* test/lisp/emacs-lisp/testcover-resources/testcases.el
(testcover-testcase-nth-case):
* test/lisp/ffap-tests.el (ffap-ido-mode):
* test/lisp/files-tests.el (file-test--do-local-variables-test):
* test/lisp/net/tramp-tests.el (tramp--test-utf8):
* test/lisp/progmodes/elisp-mode-tests.el
(find-defs-defgeneric-eval, find-defs-defun-eval)
(find-defs-defvar-eval, find-defs-face-eval)
(find-defs-feature-eval): Give 'eval' non-nil LEXICAL argument.
* test/lisp/subr-tests.el
(subr-tests--dolist--wrong-number-of-args):
* test/src/eval-tests.el (eval-tests--if-dot-string)
(eval-tests--mutating-cond)
(eval-tests-19790-backquote-comma-dot-substitution): Test 'eval'
using LEXICAL as both nil and non-nil.
(eval-tests--let-with-circular-defs): Give explicit nil to 'eval'.