add rget/rput in comm_backend

[JiakunYan]

The first step towards implementing the converse one-sided API.

The exact interface might be slightly tweaked once @adityapb copies the converse-layer logic here.

Also remove the deprecated LCI1 backend and bump the LCI2 autofetch tag.

[Copilot]

Pull Request Overview

This PR introduces the converse one-sided API by renaming the active message functions (sendAm → issueAm) and adding remote get/put operations (issueRget and issueRput).

• Update comm_core functions to use the new Status field local_buf instead of msg.
• Add and implement issueRget, issueRput, and getRKey functions in the LCI2 and internal backend layers.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/convcore.cpp	Updated message handling to use local_buf and renamed sendAm to issueAm.
src/comm_backend/lci2/comm_backend_lci2.h	Changed API declarations: removed sendAm, added issueAm, issueRget, issueRput, and getRKey.
src/comm_backend/lci2/comm_backend_lci2.cpp	Updated function implementations to match API changes (issueAm, issueRget, issueRput, getRKey).
src/comm_backend/comm_backend_internal.h	Updated virtual API signatures to reflect new function names and additions.
src/comm_backend/comm_backend_internal.cpp	Updated wrapper functions to call issueAm, issueRget, issueRput, and getRKey.
src/comm_backend/comm_backend.h	Updated API documentation to rename sendAm to issueAm, and added issueRget, issueRput, and getRkey.

Comments suppressed due to low confidence (1)

src/comm_backend/comm_backend.h:68

• The function name 'getRkey' uses different casing compared to 'getRKey' in other backend files. Consider standardizing the naming convention to avoid potential confusion.

rkey_t getRkey(mr_t mr);