feat: add loadHex function for SparseMemory

[hanm2019]

Closes #1014

Context, Motivation & Description

the SparseMemory in lib/src/main/scala/spinal/lib/bus/amba4/axi/sim/AxiMemorySim.scala has a function loadbin() so that in the simulation, we can init the memory through bin file. It may be more convenient that offer a function loadHex(), so that we can directly init the memory by hex file

Impact on code generation

Has no impact on code generation, this function impact the simulation of AxiMemorySim

However, I am not sure the implement of loadHex() is right, would you please review this code, I have test this function on a hex file.

Checklist

• Unit tests were added
• API changes are or will be documented:
  • using Scaladoc comments: /** */?
  • on RTD?
  • thanks to a new tracking issue on RTD?

[hanm2019]

I also update the readHexFile function in HexTools.
In my opinion, the HexOffset may bigger than 0x80000000, If the datatype of HexOffset is int, this value will exceed the value range of int. Maybe use Long is better.
I also update the hToI function with the same reason.

for example. In hex file, there is a line:

:02 00 00 04 8000 7A

this line means that the offset will change to 0x8000 << 16. If the hToI use Integer.parseInt to parse this string, It will get -2147483648, not the 2147483648.

[kleinai]

Makes sense. Is this ready to merge now?

[Readon]

Is that possible to add some test for this? It would be good in two points.

1. help user to know how to use it.
2. ensure code is working as expected.

[hanm2019]

Is that possible to add some test for this? It would be good in two points.

1. help user to know how to use it.
2. ensure code is working as expected.

I have add some test for loadHex