[Bug] Avoid IHttpContextAccessor as much as possible.

[jmprieur]

Which Version of Microsoft Identity Web are you using ?
Microsoft Identity Web 0.1.5-preview

Repro
Avoid IHttpContextAccessor as much as possible:

• It gives a false sense of security. Everywhere where we can access the HttpContext directly we should do so. It’s not obvious in the multi-threaded methods that they use the HttpContext (which is not thread safe). Hiding that we use it leads to unsafe use.
• A lot of time, the HttpContext is passed to access one field. There is a balance between the simple developer experience and
  the safety. Secretly accessing the HttpContext is not on the right side of the balance. For instance:
  ReplyForbiddenWithWwwAuthenticateHeader should pass in the HttpContext rather than relying on the accessor, it's called directly from a controller anyways (See TokenAcquisition.cs#L506)

requires more spec.

[jmprieur]

@jennyf19 : the work you've been doing on adding suggested cache key in the TokenSerializationArgs will remove a lot of this work

[jmprieur]

Blocked until we have the cacheKey for the token cache providers.

[jmprieur]

Verified we've removed all what we could.

[jennyf19]

Included in 0.2.0-preview release