Extend --link flag to support explicit kinds

[gayanW]

This PR extends --link option to support both the formats "kind|title=url" and "title=url"

Example usages:

Custom links:

launchable record build --name $build --link 'Title 1=https://google.com' --link 'Title 2=https://bing.com'`

Invalid kind:

$ launchable record build --name $build --link 'GITHUB_PR|PR=https://github.com/launchableinc/cli/pull/1'
Invalid kind 'GITHUB_PR' passed to --link option.
Supported kinds are: ['CUSTOM_LINK', 'JENKINS', 'GITHUB_ACTIONS', 'GITHUB_PULL_REQUEST', 'CIRCLECI']

Invalid URL for kind:

$ launchable record build --name $build --link 'GITHUB_PULL_REQUEST|PR=https://github.com/launchableinc/cli/pull/1/files'
Invalid url 'https://github.com/launchableinc/cli/pull/1/files' passed to --link option.
URL doesn't match with the specified kind: GITHUB_PULL_REQUEST

Infer kind:

$ launchable record build --name $build --link PR=https://github.com/launchableinc/cli/pull/1

GitHub PR links are automatically inferred as GITHUB_PULL_REQUEST.

Prioritize link options over env links:

$ GITHUB_PULL_REQUEST=https://github.com/launchableinc/cli/pull/1
$ launchable record build --name $build --link 'GITHUB_PULL_REQUEST|PR=https://github.com/launchableinc/cli/pull/2'

Here GITHUB_PULL_REQUEST URL passed in the link option will be used instead of the URL set via the environment variable.

[ono-max]

I'll review this PR by this weekend.

[ono-max]

Can you add the prefix _ to the private methods for expressing they're private?

e.g. https://github.com/cloudbees-oss/smart-tests-cli/blob/main/launchable/testpath.py#L46

[ono-max]

Should we handle the whitespace?

e.g. GITHUB_PULL_REQUEST | PR = https://github.com/launchableinc/cli/pull/2

[gayanW]

I don't have a strong opinion on this. I stripped the values to be forgiving to user error.

[ono-max]

Can we use the named group? Here is the example:

>>> p = re.compile(r'(?P<word>\b\w+\b)')
>>> m = p.search( '(((( Lots of punctuation )))' )
>>> m.group('word')
'Lots'
>>> m.group(1)
'Lots'

[gayanW]

Since we are not extracting any parts of the URL, I think it's better to keep it simple.