Updates and reorganization of deployment guides

[brooke-hamilton]

Description

This PR contains documentation updates, including:

• Consolidation of Bicep deployment instructions into a new docs/deployment-guide-bicep.md file.
• Moved and updated the terraform deployment instructions into docs/deployment-guide-terraform.md.
• Implemented a standard table of contents in the Terraform and Bicep deployment docs.
• Updated the README.md docs at src/terraform and src/bicep to link to the deployment guides.
• Generated a list of parameters for the Bicep folder documentation at src/bicep/README.md.
• Removed unused images at docs/images/custom_template_deployment.gif, docs/images/missionlz_as_of_july2021.jpg, and docs/images/missionlz_as_of_may2021.png

Issue reference

The issue this PR will close: #562
The issue this PR will close: #428
The issue this PR will close: #299 (See the Azure Firewall Premium section in deployment-guide-bicep.md.)

Checklist

Please make sure you've completed the relevant tasks for this PR out of the following list:

• All acceptance criteria in the backlog item are met
• The documentation is updated to cover any new or changed features
• Manual tests have passed
• Relevant issues are linked to this PR

[glennmusa]

🎉