AVM: Track Scratch Slot Types

[iten-alg]

Summary

This PR will allow us to error on things of the sort:
"byte 0x01; store 0; int 1; load 0; +"
by keeping track of the scratch space as we assemble the program within each basic block.

Test Plan

Load/Store: Tested to make sure a load in the first block puts a uint64 on the stack and that load puts the type of whatever was last stored in that slot if a store was done in that block

Loads/Stores: Added test for loads when all the slots are the same type and put in a test for stores which makes sure it only sets slots to StackAny if the type is not the same as what's on the stack

[codecov]

Codecov Report

Merging #4064 (962b55f) into master (8088e04) will increase coverage by 0.01%.
The diff coverage is 81.57%.

@@            Coverage Diff             @@
##           master    #4064      +/-   ##
==========================================
+ Coverage   54.39%   54.40%   +0.01%     
==========================================
  Files         391      391              
  Lines       48570    48594      +24     
==========================================
+ Hits        26418    26436      +18     
- Misses      19929    19936       +7     
+ Partials     2223     2222       -1     

Impacted Files	Coverage Δ
data/transactions/logic/opcodes.go	84.86% <ø> (ø)
data/transactions/logic/assembler.go	83.31% <81.57%> (+0.16%)	⬆️
ledger/blockqueue.go	82.18% <0.00%> (-2.88%)	⬇️
ledger/tracker.go	74.45% <0.00%> (-2.17%)	⬇️
catchup/peerSelector.go	98.95% <0.00%> (-1.05%)	⬇️
cmd/tealdbg/debugger.go	72.69% <0.00%> (-0.81%)	⬇️
network/wsNetwork.go	62.79% <0.00%> (-0.20%)	⬇️
ledger/acctupdates.go	69.43% <0.00%> (+0.65%)	⬆️
data/transactions/verify/txn.go	45.02% <0.00%> (+0.86%)	⬆️
cmd/algoh/blockWatcher.go	80.95% <0.00%> (+3.17%)	⬆️
... and 1 more

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[jannotti]

Looks good to me. I'd like @michaeldiamant to have a look on Monday when he comes back as I think he's the only other person who has looked at ProgramKnowledge.