fix: false positives for static expressions in detect-non-literal-fs-filename, detect-child-process, detect-non-literal-regexp, and detect-non-literal-require

[ota-meshi]

This PR improves 4 rules and changes them to track the expression used and not report when it is a static value.

They will no longer be reported after the change in this PR.

import fs from 'fs';
import path from 'path';
const html = fs.readFileSync(path.resolve(__dirname, './index.html'), 'utf-8');
                          // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

import url from "url";
const dirname = path.dirname(url.fileURLToPath(import.meta.url));
const html = fs.readFileSync(path.resolve(dirname, './index.html'), 'utf-8');
                          // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

const pkg = fs.readFileSync(require.resolve('eslint/package.json'), 'utf-8');
                         // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

const config = require(process.cwd() + '/foo.config.js');
                    // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

import child_process from 'child_process';
const FOO = 'ls';
child_process.exec(FOO);
                // ^^^

const source = 'ab+c'
const a = new RegExp(source, 'i')
                  // ^^^^^^

---

close #65
close #49
related to #22

[nzakas]

#108 has been merged.

[ota-meshi]

I have rebased this PR!

[nzakas]

LGTM. Thanks!