* As this very useful document describes [1]
the BIOS first checks the prid of COP0 to decide
whether to execute the IOP or EE boot sequence.
Without this the BIOS doesn't execute the code we want.
The code sequence that determines this is added below as
suedo assembly

MFC0: GPR[26] = COP0_REG[15] /* Load cop0 prid to GPR 26 */
SLTI: GPR[1] = GPR[26] < 89 /* Check if its value is less than 0x59 and store the bool in GPR 1 */
BNE: if GPR[0] != GPR[1] then pc += 20 /* If the comparison is true then jump +20 to IOP */

[1] https://rust-console.github.io/ps2-bios-book/print.html
[2] https://psi-rockin.github.io/ps2tek/#biosbootprocess

In addition:
* Correct register notation (word refers to a 32bit quantity not 16bit)
* Simplify sign extension casing
* Add more useful logging

* MIPS has an architectural feature, where instead of flushing the
pipeline when executing a branch instruction, it goes ahead and executes
the instruction following the branch as well. Flushing the pipeline
is costly and is the cause of those complex branch predictors on
modern CPUs that try to guess when a branch will be taken.

* To properly emulate this behaviour we must act how the pipeline acts. We
will always have 2 instructions loaded the current one and the next one. This way
we can load the instruction after the branch even though the pc changes.

* The instruction decoding was based on the handy table in ps2tek [1]
while the instructions themselves were written based on the document
added.

* The implementation makes heavy use of bitfields and unions in C++ to
make accessing different bits/sections of registers easier and more
intuitive. You may also notice the frequent casting (uint32_t)(int16_t)
which might seem useless but is there to force the compiler to generate
instructions to sign extend the offsets.

[1] https://psi-rockin.github.io/ps2tek/#eeinstructiondecoding

* Now that the BIOS is loaded we can start executing it!
The starting address the EE uses is 0xbfc00000 which maps
to KUSEG1. Since all KUSEG regions except KUSEG2 are mirrors
of each other we only need to translate the address to the
KUSEG appropriate.

* The functional differences between KUSEG0/1 are minimal and
very niche so I won't bother emulating them now. Address wise
we can notice that the only difference between addresses is the
most significant half byte. By using that byte as an index in
a mask table we can define an appropriate mask for each KUSEG
address. Idea taken from a very handy PSX document I discovered
last year [1]

[1] https://svkt.org/~simias/guide.pdf (43)

* This commit adds a most basic CPU class that acts as a template
which we will slowly build.

* The architecture is pretty simple; the ComponentManager will create all
the seperate components (EE, VP, IOP, GS etc) as unique_ptr's since
it owns them and only it has access to them. All the other components
must pass through the manager to read/write data to memory.
To achieve this they are given a pointer to the ComponentManger in their constructor.

* For now the CPU directly accesses the bios which shouldn't
happen but will be fixed eventually when I implement generic
read/writes. The goal is to start implementing the CPU as fast as
possible in order to get to the GPU/VPU's and display something!