Fixes #2953.

This reverts commit e3ab1276, reversing
changes made to f988b0a6.

We prefer to test across all platforms at once with
`SchemaManagerFunctionalTestCase::testEscapedDefaultValueMustBePreserved()`
rather than to test only a single specific platform.

It is now possible to use `\` in non-escaped default values for a column,
and it will be automatically escaped for platforms that need it.

Previously this lead to a confusion when diffing actual and expected
schema leading to perpetual out of sync schema.

Before:

```php
/**
 * @ORM\Column(options={"default" = "Foo\\Bar"}))
 */
private $name;

```

After:

```php
/**
 * @ORM\Column(options={"default" = "Foo\Bar"}))
 */
private $name;

```

And the result in database will be a default value exactly as written in
the annotation, that is `Foo\Bar`.

People that are starting a new project will immediately know what this
is about, but people upgrading doctrine might get a lot of these and
should have a better clue regarding what this is about.

People do not need to know that this will be implemented as an
exception.

I am not sure if there is a rationale behind ignoring extra keys like
this. I was under the impression that something might copy options to
platform specific options, thus leaving options in the original array,
knowing they would be ignored anyway. If it is the case, it would be
best to just move them, otherwise, this commit might help troubleshoot
some mapping issues.
I had to fix some tests that wrongly used that options array (maybe
these options were valid at some point?).

Added test case for PHP Resource as parameter in Driver exception

The reasoning behind this is to essentially rely on a single type (or
the absence of it), therefore add type declarations.

Since these are private methods we can do that without breaking BC.