aconfig: create aconfig_storage_file binary to print the storage files

To help debug storage files. We need a binary to parse the storage
binary files and print out the flag values like device_config list
command. In addition, aconfig_storage_file needs to provide a public api
to allow flag cli to call to get the flag values. Therefore creating
this change.

This change includes the following changes:

1, Implement debug print trait for package table, flag table, and flag
value struct. So the debug dump is more readable.

2, Add a list flag api to create a vector of flag name and value tuples
given the storage file names. This api will be used by
aconfig_storage_file binary as well as aconfig flag cli.

3, Add a main.rs to create aconfig_storage_file binary to debug print
storage files or list all the flags in storage files. It has two
subcommands.

3.1 print command:
aconfig_storage_file print --file <storage file> --type
<package_map|flag_map|flag_val>

This command produce a debug print of a single the storage file content

3.2 list command:
aconfig_storage_file list --package_map <package map file> --flag_map
<flag map file> --flag_val <flag value file>

This command parses all storage files to print out list of flag values
in the following form:

<package>/<flag>, <value>
...
<package>/<flag>, <value>

Bug: b/321077378
Test: manual test of the binary command
Change-Id: I000e216d13854f853cbd9b63cabb6db3a47dbece