Reduce memory consumption of SLEIGH plugin

[FXTi]

Problem:

• In default, after full init, SLEIGH plugin will take extra ~80M memory.
• For SleighInstruction, one instruction will take ~20K.

Solution:

• Try to reduce arch info stored in memory during parsing spec file
• Isolate InstructionContext from SleighInstruction like Java version of Ghidra do

Time:

Will do this in the middle of Sep.

Plan:

• [x] As above

• [ ] Add detailed test cases(ESIL extension, P-code->ESIL translation, type identification)

• [ ] Fix on Dex parse

• [ ] Redo hard-coded map of SN and BP (https://github.com/radareorg/r2ghidra-dec/pull/120#discussion_r479974366)

• [ ] Type identicication of float number

HELP NEEDED Still problem in FP to mem, mem to FP (Because I'm not familiar with low level mem mechanism of Radare2)

[0x00000000]> e asm.arch=x86
[0x00000000]> e asm.bits=32
[0x00000000]> pdga
[0x00000000]> "ae 7,0x0,=[8]"
[0x00000000]> "ae 0x0,[8]"
0x7
[0x00000000]> "ae 7,I2F,0x0,=[8]"
[0x00000000]> "ae 0x0,[8]"
0x401c000000000000
[0x00000000]> "ae 7,I2F,512,=[8]"
[0x00000000]> "ae 512,[8]"
0x401c000000000000
[0x00000000]> "ae 7,I2F,512+8,=[8]"
[0x00000000]> "ae 512+16,[8]"
0x401c000000000000
[0x00000000]> "ae 512+32,[8]"
0x401c000000000000
[0x00000000]> 

[FXTi]

https://github.com/rizinorg/rz-ghidra/commit/5be31a8ce3e35b46bbd451bccd20afe8d70c0df8 Doubt if this modification is proper.