[FEA] Add support for typed constant in debug info metadata emission.

[jiel-nv]

Add support for typed constants in debug info metadata fields (like extraData in DIDerivedType):

e.g.
!8 = !DIDerivedType(tag: DW_TAG_member, ... , extraData: i32 1)
or
!24 = !DIDerivedType(tag: DW_TAG_member, ... , extraData: i8 2)

The extraData field should be LLVM IR ConstantAsMetadata wrapping a typed constant (like ConstantInt) in LLVM IR text format which appears as typed constants like:
i32 1
i8 2

Also add a llvmlite test to guard this change.

I have tested this change with the Numba and Numba-CUDA debuginfo tests locally as well, with no issues.

[jiel-nv]

The CI failure should be cleared once PR#1325 is in. @swap357
Could you please review this change? @gmarkall

[swap357]

The CI failure should be cleared once PR#1325 is in. @swap357 Could you please review this change? @gmarkall

Thank you for the PR, @jiel-nv.
about CI failures, I do not think PR#1325 has anything to do with PR checks being run here. From logs here -
https://dev.azure.com/numba/numba/_build/results?buildId=19979&view=logs&j=c32913f0-c98d-5e24-2f8e-6294d1cfd8e0&t=66f0d9e4-d5b5-5af3-0bcb-f619e9fb3708&l=182
they seem to be flake8 errors that might need correction on patch itself

[jiel-nv]

Thank you for the PR, @jiel-nv. about CI failures, I do not think PR#1325 has anything to do with PR checks being run here. From logs here - https://dev.azure.com/numba/numba/_build/results?buildId=19979&view=logs&j=c32913f0-c98d-5e24-2f8e-6294d1cfd8e0&t=66f0d9e4-d5b5-5af3-0bcb-f619e9fb3708&l=182 they seem to be flake8 errors that might need correction on patch itself

Thank you @swap357. I've submitted a fix.

[gmarkall]

Thanks for the PR - this looks good to me. I've checked it aligns with other IR documented in the LLVM Language reference manual, e.g. https://llvm.org/docs/LangRef.html#ditemplatevalueparameter which gives value: i32 7 as an example. I also notes that the use of typed constants is consistent with general usage in metadata nodes (c.f. https://llvm.org/docs/LangRef.html#metadata-nodes-mdnode).