Add functions to clear breadcrumbs and bulk set tags and extras in the scope

[ste93cry]

Q	A
Branch?	2.2 (develop)
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
License	MIT

This closes #797 by implementing the setTags, setExtras and clearBreadcrumbs methods on the Scope class. I also refactored the tests to stop relying on reflection to access the active scope of an hub. I wonder if it makes sense to deprecate all the getters on the scope as the other SDKs do not implement them

[HazAT]

Thanks!

[ste93cry]

@HazAT should we deprecate the getters on the Scope class and discourage their usage?

[HazAT]

@ste93cry Yes, we could add @deprecated before we make them protected or something.

[ste93cry]

Since they are marked as @internal we can remove them immediatly without breaking BC per PHPDoc-definition as they should not be used outside the application or library:

The @internal tag is used to denote that associated Structural Elements are elements internal to this application or library