Add missing locks in console.c and proc.c

[ahilaan]

This PR adds the missing locks to console.c and proc.c, as mentioned in #214 :

Changes made in console.c:

• Added locking in consoleintr() around shared console input buffer state
• Ensured consoleintr() releases the console lock before calling procdump()
• Added locking in consolewrite() to serialize console output

Changes made in proc.c:

• Fixed allocproc() failure paths so p->state = UNUSED is updated under ptable.lock

Notes:

• I did not add cons.lock around the waiting loop in consoleread(). If consoleread() holds cons.lock while waiting for input.r != input.w, then consoleintr() cannot acquire the same lock to insert new input into the buffer, thus creating a deadlock.
• All files have not been checked thoroughly for missing locks in this PR, so they may need to be added in subsequent PRs

[codenet]

Hey, actually the locks that you added in proc.c are unnecessary as we made the process EMBRYO within the lock. Two instruction sequences shall not reach found with the same p.

I also removed locks from interrupt handlers such as consoleintr as interrupts are anyways disabled inside interrupt handlers. I added locks in consolewrite here: d0b7ccd

cc @illuminati2285