Implement Processor API and associated Cortex underlying implementations

[emrainey]

The processor Interface should allow access to some information about the Chip and the allow some control.

namespace jarnax {

/// @brief The interface to the Processor
class Processor {
public:
    /// @brief Disable Interrupts
    virtual void DisableInterrupts() = 0;
    /// @brief Enables Interrupts
    virtual void EnableInterrupts() = 0;
    /// @brief Gets the current system tick count
    virtual cortex::Ticks GetTicks() const = 0;
    /// @brief Gets the Cortex Part Number
    virtual cortex::PartNumber GetPartNumber() const = 0;
    /// @brief Gets the Cortex Revision Number
    virtual cortex::Revision GetRevision() const = 0;
    /// @brief Gets the Frequency of the Core.
    virtual cortex::Hertz GetCoreFrequency() const = 0;
    /// @brief Gets the Frequency of the clock which feeds the System Tick
    virtual cortex::Hertz GetSystemTickClockFrequency() const = 0;
    /// @brief Gets the Priviledged Mode
    virtual cortex::modes::Privileged GetMode() const = 0;
    /// @brief Resets the Processor
    /// @warning This method will not return!
    virtual void SoftwareReset() = 0;

protected:
    ~Processor() = default;
};
}    // namespace jarnax

[emrainey]

GetMode() may not be kept as I think it's a privileged call to get the CONTROL register? Need to read up on that.

[emrainey]

https://developer.arm.com/documentation/dui0646/c/The-Cortex-M7-Processor/Programmers-model/Core-registers

Indicates that Handlers might be able to use it, but they are already inside the privileged boundary, so we can probably remove GetMode() as Thread Mode can't read CONTROL without a fault.

[emrainey]

Pushed a develop version to the develop branch. There'll be some on target testing done before I close this.