Add label to extension analyze API

[cd-work]

This adds the new label option as the last optional parameter of the analyze function, allowing phylum-ci to use the extension API for its analysis.

Closes #1131.

[cd-work]

I plan to remove the extension itself before merging this, since it's probably better to have it in the phylum-ci repository. However this should make testing easier.

[maxrake]

Local testing has not been performed yet...but it will be if/when the suggested changes are made.

[maxrake]

The changes were tested locally and found to work with phylum-ci after a few changes were made in that repo. The real trick is making a ci extension available in the phylum-ci Docker image.

The current method for making phylum available in the image relies on the custom/hidden --global-install option. Something similar may have to be done for this extension since the expectation is that using phylum extension install will result in an extension installed in the root user's directory and then not be available to non-root users.

Perhaps the extension could be copied manually to a globally accessible directory (like the binary is) and then accessed with a phylum extension run command instead of a phylum ci command.

[cd-work]

Something similar may have to be done for this extension since the expectation is that using phylum extension install will result in an extension installed in the root user's directory and then not be available to non-root users.

Can't you just install it as root?

[maxrake]

Can't you just install it as root?

Maybe...if the permissions can also be changed to allow access by non-root users. There are some environments...like Azure Pipelines...where a container is created from the image with a non-root user. From previous issue covering this:

This is a problem for some CI environments. For instance, Azure Pipelines creates containers from a given image with a user named vsts_azpcontainer and an id of 1001, in a group named azure_pipelines_sudo. Tasks/scripts/commands run from that container are done so with this user, which doesn't have access to the /root/.local/bin directory where the phylum Python package script entry points are located.

[maxrake]

The example ci extension has been tested and shown to work in the phylum-ci repo. It can be removed from this PR now if that is still the plan. The rest of the code changes in this PR are desired in a release candidate for use in a new phylum-ci release.

[cd-work]

I've moved the extension to phylum-dev/phylum-ci#267 for now.

[maxrake]

LGTM.