Extend the tests in regexp/inspect_spec with over escaping combined with character classes

先从 regexp/inspect_spec 和现有的 escaped backslash 示例开始，然后检查 language/case_spec 中 interpolated-regexp 的行为。为列出的 backslash 和 character-class 情况添加覆盖，并添加一个明确的 embedded-regexp 示例；相关 specs 应在不改变 case 语句行为的情况下通过。

The specs have one test for escaped backslashes in Regexp#inspect:

it "does not over escape" do
  Regexp.new('\\\/').inspect.should == "/\\\\\\//"
end

The obvious implementation to make this spec pass is to simply escape every slash with another slash. This works in this case, but that causes an error in language/case_spec for something that is not related to the case statement:

it "tests with a regexp interpolated within another regexp" do
  digits_regexp = /\d+/
  case "foo43"
  when /oo(#{digits_regexp})/

This results in a regexp /oo(?-mix:\\d+)/, which now expects a slash followed by one or more d characters. This does not match the input, but does not indicate the escaping as the issue.

I tested my implementation with the these specs added, but this was more or less brute forcing every possibility. Also, because Regexp.new takes a String which has an additional layer of escaping, I peferred the // notation.

Regexp.new('\d+').inspect.should == "/\\d+/"
/\d+/.inspect.should == "/\\d+/"

Regexp.new('\\d+').inspect.should == "/\\d+/"
/\\d+/.inspect.should == "/\\\\d+/"

Regexp.new('\\\d+').inspect.should == "/\\\\d+/"
/\\\d+/.inspect.should == "/\\\\\\d+/"

Regexp.new('\\\\d+').inspect.should == "/\\\\d+/"
/\\\\d+/.inspect.should == "/\\\\\\\\d+/"

I think it would be better to at least include the following cases:

/\d+/ # Output should have 1 not escaped slash, since this should not be escaped
/\\d+/ # Output should have 1 escaped slash (so 2 slashes), this should be escaped
/\\\d+/ # Output should have 1 escaped and 1 not escaped slash (so 3 slashes)

Furthermore, I think it would be better to add an explicit test for the regexp embedded in regexp scenario like there is in the case spec now, just to make the test a bit more explicit and decouple it from the case statement.

I'm not that familiar with this project and how things are structured, can I just add a few tests to the inspect spec of regexp, and make a new spec file for the embedding tests?