FullyQualifiedName does not properly escape special characters

Running an individual test that has a special character in its name will bomb due to the character not being escaped. For example:

```
[]
let ``Say Hi!`` () =
hello |> Assert.True(true)
```

will result in the following error:

```
C:\fsharp\hello-world>dotnet test --logger "trx;LogFileName=C:\Temp\test-explorer-KLRHlK\Results.trx" --filter "FullyQualifiedName~HelloWorldTest.Say Hi!"
Build started, please wait...
Build completed.

Test run for C:\fsharp\hello-world\bin\Debug\netcoreapp2.0\HelloWorld.dll(.NETCoreApp,Version=v2.0)
Microsoft (R) Test Execution Command Line Tool Version 15.7.0
Copyright (c) Microsoft Corporation. All rights reserved.

Starting test execution, please wait...
[xUnit.net 00:00:00.3667942] HelloWorld: Exception filtering tests: Incorrect format for TestCaseFilter Error: Invalid Condition 'FullyQualifiedName~HelloWorldTest.Say Hi!'. Specify the correct format and try again. Note that the incorrect format can lead to no test getting executed.
No test matches the given testcase filter `FullyQualifiedName~HelloWorldTest.Say Hi!` in C:\fsharp\hello-world\bin\Debug\netcoreapp2.0\HelloWorld.dll

Additionally, path to test adapters can be specified using /TestAdapterPath command. Example /TestAdapterPath:.
```

This is because the `--filter` is `FullyQualifiedName~HelloWorldTest.Say Hi!`, and the `!` is a special character. Running the same command manually with it escaped works fine:

```
C:\fsharp\hello-world>dotnet test --logger "trx;LogFileName=C:\Temp\test-explorer-KLRHlK\Results.trx" --filter "FullyQualifiedName~HelloWorldTest.Say Hi\!"
```

It looks like the special characters `!`, `=`, `|`, and `&` (and possibly others) need to be escaped if they exist in the test name.