Create separate api for reconciling per-sdk storage

Sdks should get their own storage area under the sdk package path
at: `/data/misc_ce/0/sdksandbox/<package>/<sdk-name>@<random-suffix>`

The random suffix is to prevent sdks from guessing each others storage
paths. It is separated by '@' which is an illegal character for package
names.

The new API prepares the sdk-level directories as follows:
- creates them if they do not exist.
- on occasssions where they already exist, it skips creating them.
- on occasssions where it finds an per-sdk directory that shouldn't be
  there, it deletes them.
- it also creates the package path if its missing for any reason.

Additional Changes:
- For package-level sdk data directory, we now delete it if FLAG_STORAGE_SDK
flag is not passed. This is done so that we clean up properly when an
app that consumes sdk updates to a state where it no longer consumes
sdks.

Bug: 211763739
Test: atest installd_service_tes
Test: atest SdkSandboxStorageHostTest
Ignore-AOSP-First: Feature is being developed in internal branch
Change-Id: I7f144f5da4c4e10851f78d731de5dfb429fbac4d