[libc] Add proxy headers for ENTRY, ACTION, VISIT, and hsearch_data.

[lntue]

For hsearch_data, we should also remove the 2 unused fields in the definition, since under full build mode, we don't need to match with glibc ABI.

• ENTRY: [libc] Add proxy header for ENTRY type. #139746
• ACTION: [libc] Add proxy header for ACTION type. #139796
• VISIT
• hsearch_data

[llvmbot]

@llvm/issue-subscribers-libc

Author: None (lntue)

[lntue]

@enh-google