[CLI] Add "ti cache clean" command to clean the offline cache files manually

[PGZXB]

Issue: #6919

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[lin-hitonami]

LGTM! some nits:

[PGZXB]

Should we add an error message here?

Thanks for your suggestion ~
I added some hint messages.

• ti cache

[Taichi] version 1.4.0, llvm 15.0.1, commit 02cce8c6, win, python 3.7.0
[I 12/21/22 21:06:27.015 70128] [shell.py:_shell_pop_print@23] Graphical python shell detected, using wrapped sys.stdout

*******************************************
**      Taichi Programming Language      **
*******************************************

Docs:   https://docs.taichi-lang.org/
GitHub: https://github.com/taichi-dev/taichi/
Forum:  https://forum.taichi.graphics/

usage: ti cache <command> [<args>]
        clean   |-> Clean all offline cache files in given path
>>> Running time: 0.00s

• ti cache faker

[Taichi] version 1.4.0, llvm 15.0.1, commit 02cce8c6, win, python 3.7.0
[I 12/21/22 21:07:32.127 67672] [shell.py:_shell_pop_print@23] Graphical python shell detected, using wrapped sys.stdout

*******************************************
**      Taichi Programming Language      **
*******************************************

Docs:   https://docs.taichi-lang.org/
GitHub: https://github.com/taichi-dev/taichi/
Forum:  https://forum.taichi.graphics/

'ti cache faker' is not a valid command!
usage: ti cache <command> [<args>]
        clean   |-> Clean all offline cache files in given path
>>> Running time: 0.00s

• ti cache clean

[Taichi] version 1.4.0, llvm 15.0.1, commit 02cce8c6, win, python 3.7.0
[I 12/21/22 21:10:11.792 36964] [shell.py:_shell_pop_print@23] Graphical python shell detected, using wrapped sys.stdout

*******************************************
**      Taichi Programming Language      **
*******************************************

Docs:   https://docs.taichi-lang.org/
GitHub: https://github.com/taichi-dev/taichi/
Forum:  https://forum.taichi.graphics/

Deleted 9841 offline cache files in C:\taichi_cache\ticache
>>> Running time: 1.87s

• ti cache clean faker

[Taichi] version 1.4.0, llvm 15.0.1, commit 02cce8c6, win, python 3.7.0
[I 12/21/22 21:12:10.007 70904] [shell.py:_shell_pop_print@23] Graphical python shell detected, using wrapped sys.stdout

*******************************************
**      Taichi Programming Language      **
*******************************************

Docs:   https://docs.taichi-lang.org/
GitHub: https://github.com/taichi-dev/taichi/
Forum:  https://forum.taichi.graphics/

usage: ti cache clean [-h] [-p OFFLINE_CACHE_FILE_PATH]
ti cache clean: error: unrecognized arguments: faker

• ti cache clean -p ./2022-12-21-JOC/gfx

[Taichi] version 1.4.0, llvm 15.0.1, commit 02cce8c6, win, python 3.7.0
[I 12/21/22 21:13:17.783 33348] [shell.py:_shell_pop_print@23] Graphical python shell detected, using wrapped sys.stdout

*******************************************
**      Taichi Programming Language      **
*******************************************

Docs:   https://docs.taichi-lang.org/
GitHub: https://github.com/taichi-dev/taichi/
Forum:  https://forum.taichi.graphics/

Deleted 15 offline cache files in D:\CODE\CPP_CODE\taichi_test\2022-12-21-JOC\gfx
>>> Running time: 0.00s

[lin-hitonami]

LGTM