Add `physicalFilename` option into rule tester

@snitin315 @nzakas @mdjermanovic

I find physicalFilename is not available in ValidTestCase, so it makes testing cases for virtual filename unavailable, should that be supported?

Before context.getPhysicalFilename, I have a custom util getPhysicalFilename and a test case like:

ruleTester.run('remark', remark, {
  valid: [
    {
      code: '<header>Header2</header>',
      parser,
      parserOptions,
      filename: path.resolve(__filename, '0-fake.mdx'), // virtual filename
    },
  ],
})

But when I migrate to context.getPhysicalFilename, it results context.getPhysicalFilename() === filename, it is not correct, so maybe a new physicalFilename option is required for this case:

ruleTester.run('remark', remark, {
  valid: [
    {
      code: '<header>Header2</header>',
      parser,
      parserOptions,
      physicalFilename: __filename,
      filename: path.resolve(__filename, '0-fake.mdx'), // virtual filename
    },
  ],
})

_Originally posted by @JounQin in https://github.com/eslint/eslint/issues/14616#issuecomment-878712207_

[btmills]

It sounded like mysticatea had a couple changes planned for the existing RFC, so I left a comment inquiring what those might be before I make any changes of my own, but I haven’t heard back. I’ll go ahead and update it for review by the team.

[btmills]

In the most recent TSC meeting, we agreed to go with the approach described in RFC31. I’ll be picking up that RFC to update it as necessary and get it through approval.