Escape special characters in section name of editor config

[captainsafia]

Addresses part of #52469.

[Youssef1313]

I added the ConfigWithEscapedValues in AnalyzerConfigTests to validate that the SectionNameLexer correctly processes the escaped values but it doesn't seem like the Parse helper in the AnalyzerConfigTests actually calls this codepath? It looks like it stops processing the section name here.

I believe this code path is covered by when you call TryCreateSectionNameMatcher, which should be already covered in tests. For example this test:

roslyn/src/Compilers/Core/CodeAnalysisTest/Analyzers/AnalyzerConfigTests.cs

Lines 401 to 411 in cf42e6b

	[Fact]
	public void LiteralBraces()
	{
	SectionNameMatcher matcher = TryCreateSectionNameMatcher("abc\\{\\}def").Value;
	Assert.Equal(@"^.*/abc\{}def$", matcher.Regex.ToString());
	Assert.True(matcher.IsMatch("/abc{}def"));
	Assert.True(matcher.IsMatch("/subdir/abc{}def"));
	Assert.False(matcher.IsMatch("/abcdef"));
	Assert.False(matcher.IsMatch("/abc}{def"));
	}

[pranavkm]

Unrelated to the issue you're trying to solve, but does this need to escape slashes (\)?

[captainsafia]

For this scenario, I tried to stick to values that were defined as special characters per the editor config specification (http://docs.editorconfig.org/en/master/editorconfig-format.html).

[chsienki]

LGTM, Thanks!