Remove duplicate account IDs and validate

[sam-cox-tracebit]

Thanks for maintaining such a useful resource!

There are some duplicate account IDs in the file due merges, mergers etc. I've found it useful to associate only a single vendor with each account ID as I nearly always want to map an account ID to a vendor rather than vice-versa. I wanted to submit a PR in case these changes would be helpful for anyone else.

I've tried to break this change down into atomic commits that can be easily verified. The summary is:

• Replace comments with source: properties where these are clearly sources
• Remove duplicate copy of "Cloudability"
• Remove "Cloud Applicatoin Manager" which duplicates CenturyLinkCloud
• Merge "Cloudtrail" into "CloudTrail" and eliminate duplicates
• Remove "Cloudyn" which duplicates "Azure Billing Management"
• Remove "Nessus AWS Connector" which duplicates "Tenable"
• Remove "Dome9 Arc" which duplicates "Checkpoint Cloudguard"
• Merge "FortiCASB" and "FortiCWP" under a new "Fortinet"
• Add a script and github action to validate that no duplicates exist and the yaml is valid (thanks to #16!)

I considered adding an "aka" property to include the duplicate names but decided to keep things simple - many of these seem to be names of previously acquired or rebranded companies.

I have not added or removed any account IDs in this process (checked by comparing against main):

% yq 'collect(.[].accounts.[]) | sort | unique | length' accounts.yaml
339
% yq 'collect(.[].accounts.[]) | sort | unique' accounts.yaml | md5sum
48752592effae9aa24bcc8151a852a8f  -

An example of the github action passing:

If you submit a PR that includes duplicates or schema validation errors:

They will fail the check:

These changes were helpful for me but I completely understand if other people use this resource differently. Also very happy to submit only a subset of these changes if requested!