aconfig_storage_read_api: make map_file function public.

With aconfigd moving to rust implementation. It not only needs to open
boot copy, but also persist and default copy. The get_mapped_file
function is meant to be used by codegen which only opens boot copy. Thus
need to make map_file function public, just like what we did in c++.

Bug: b/321077378
Test: atest
Change-Id: I4fd2a5e0cf7839fde43e83b8888488caa74fb1b9
diff --git a/tools/aconfig/aconfig_storage_read_api/src/lib.rs b/tools/aconfig/aconfig_storage_read_api/src/lib.rs
index 884f148..ab066c6 100644
--- a/tools/aconfig/aconfig_storage_read_api/src/lib.rs
+++ b/tools/aconfig/aconfig_storage_read_api/src/lib.rs
@@ -44,6 +44,7 @@
 
 pub use aconfig_storage_file::{AconfigStorageError, FlagValueType, StorageFileType};
 pub use flag_table_query::FlagReadContext;
+pub use mapped_file::map_file;
 pub use package_table_query::PackageReadContext;
 
 use aconfig_storage_file::read_u32_from_bytes;
diff --git a/tools/aconfig/aconfig_storage_read_api/src/mapped_file.rs b/tools/aconfig/aconfig_storage_read_api/src/mapped_file.rs
index 32dbed8..2c1884a 100644
--- a/tools/aconfig/aconfig_storage_read_api/src/mapped_file.rs
+++ b/tools/aconfig/aconfig_storage_read_api/src/mapped_file.rs
@@ -28,7 +28,7 @@
 /// The memory mapped file may have undefined behavior if there are writes to this
 /// file after being mapped. Ensure no writes can happen to this file while this
 /// mapping stays alive.
-unsafe fn map_file(file_path: &str) -> Result<Mmap, AconfigStorageError> {
+pub unsafe fn map_file(file_path: &str) -> Result<Mmap, AconfigStorageError> {
     let file = File::open(file_path)
         .map_err(|errmsg| FileReadFail(anyhow!("Failed to open file {}: {}", file_path, errmsg)))?;
     unsafe {