feat: improve returned error for invalid arguments

[qweeah]

What this PR does / why we need it:
This PR improves the error output when the number of input argument doesn't match expected. In the new output, user will get

1. What kind of input is expecting, as well as the usage hint
2. What's the wrong input
3. Which command to run to get more detailed examples and help

E.g. Taking oras discover as an example

# Before
$ oras discover localhost: 5000/test:demo
Error: accepts 1 arg(s), received 2
# After
$ oras discover localhost: 5000/test:demo
Error: "oras discover" requires exactly 1 argument but got 2
Usage: oras discover [flags] <name>{:<tag>|@<digest>}
Please specify exactly 1 argument as the target artifact to discover referrers from. Run "oras discover -h" for more options and examples

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #458

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.54545% with 3 lines in your changes missing coverage. Please review.

Project coverage is 80.22%. Comparing base (a377128) to head (4367ec3).
Report is 198 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/oras/root/version.go	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1201      +/-   ##
==========================================
+ Coverage   80.11%   80.22%   +0.10%     
==========================================
  Files          66       67       +1     
  Lines        3646     3681      +35     
==========================================
+ Hits         2921     2953      +32     
- Misses        511      513       +2     
- Partials      214      215       +1     

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[shizhMSFT]

LGTM

[shizhMSFT]

LGTM