cli for plumbing commands

[skshetry]

This PR introduces several plumbing CLI commands for dvc-data.

1. fsck: Checks all of the objects in the database, similar to git fsck.
2. ls: List all items of the tree, similar to git ls-tree.
3. stage: Stage, and optionally write objects to database with --write/-w. Can write in shallow mode with --shallow.
4. cat: Print contents of the object to the terminal (and optionally verify object with --check/-c.
5. p2o/o2p -> Path to oid and Oid to path.
6. genrand -> Generate file with random content (eg: ./cli.py genrand sample.txt 1GB).
7. gensparse -> Create sparse file in a portable way (eg: ./cli.py gensparse sample.txt 1GB).
8. hash -> Compute hashes of file, in --text (dos2unix) vs --binary mode, with different hashing algorithms specified via --name/-n.
   (./cli.py hash sample.txt -n blake2b --progress --text)

These are small programs meant to assist for local testing/development.

Installation

pip install -e ".[dev]"

Usage:

./cli.py <command> <args>

The default odb is created in .dvc/cache folder relative to current working directory by default. Most of the commands take --db option, that can be used to pass any alternative odb locations. You can also set ODB_PATH envvar so that you don't need to provide that again and again on the commands.
eg:

export ODB_PATH=$(mktemp -d)

[codecov-commenter]

Codecov Report

Merging #79 (baf19c0) into main (f8cf9e3) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #79   +/-   ##
=======================================
  Coverage   34.32%   34.32%           
=======================================
  Files          33       33           
  Lines        1681     1681           
  Branches      302      302           
=======================================
  Hits          577      577           
  Misses       1091     1091           
  Partials       13       13           

Impacted Files	Coverage Δ
src/dvc_data/hashfile/hash.py	59.22% <100.00%> (ø)

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