Actual immutability enforcement by placing immutable data into read-only sections

[Siarhei Siamashka]

Right now D compilers place string literals into a read-only 
section, but most of the other types of `static immutable` data 
have no protection against rogue writes.

https://forum.dlang.org/post/cmtaeuedmdwxjecpcrjh@forum.dlang.org 
is an example of a non-obvious case of immutable data corruption. 
What's happening there is that [druntime 
modifies](https://github.com/dlang/dmd/blob/v2.101.1/druntime/src/rt/deh.d#L46) the static immutable instance of Exception when throwing it.

The old bugreport https://issues.dlang.org/show_bug.cgi?id=12118 
is also related to throwing an immutable Exception, but the 
corruption is done by the user code in the catch block.

Troubleshooting such problems would have been so much easier if 
immutable objects were actually placed in a read-only section and 
any write attempts triggered segfaults at runtime. I think that 
[bare metal code for 
microcontrollers](https://forum.dlang.org/post/rkrpdgjnhwdysqnnbslf@forum.dlang.org) could also potentially benefit from this, because this would enable placing immutable data generated by CTFE into NOR flash instead of wasting SRAM space.

What do you think about it? Does this require a new DIP?