backend: (Part 1) Use DB config values for Deployments during runtime

[tianjing-li]

I noticed while working on https://linear.app/cohereai/issue/TLK-2601/add-update-to-db-config-when-app-starts that in fact the DB values for deployment configs weren't being used at all during runtime. We were instead always defaulting to what was stored in our Pydantic settings.

This PR modifies core behaviour so we store actual keys that reflect what each deployment will fetch in the newly named
get_deployment_config_var method.

AI Description

This PR introduces a new DeploymentSettingsMixin class in src/backend/config/settings.py, which formats deployment configurations before saving them to the database. The mixin class includes a to_dict method that retrieves capitalized variable names from a list of strings and returns a new dictionary with these names as keys.

The PR also renames several functions and classes to include the word "instance" in their names, indicating a shift towards working with specific instances of deployments rather than general deployment concepts. This change is reflected in the following files:

• src/backend/chat/custom/custom.py
• src/backend/chat/custom/utils.py
• src/backend/config/settings.py
• src/backend/crud/deployment.py
• src/backend/database_models/deployment.py
• src/backend/model_deployments/azure.py
• src/backend/model_deployments/bedrock.py
• src/backend/model_deployments/cohere_platform.py
• src/backend/model_deployments/sagemaker.py
• src/backend/model_deployments/single_container.py
• src/backend/model_deployments/utils.py
• src/backend/routers/utils.py
• src/backend/schemas/deployment.py
• src/backend/services/deployment.py
• src/backend/services/request_validators.py
• src/backend/tests/unit/services/test_deployment.py

Additionally, the PR adds a new function, get_deployment_by_class_name, to src/backend/crud/deployment.py, which retrieves a deployment by its class name.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.88235% with 13 lines in your changes missing coverage. Please review.

Project coverage is 77.26%. Comparing base (d966233) to head (bf071db).

Files with missing lines	Patch %	Lines
src/backend/chat/custom/utils.py	25.00%	3 Missing ⚠️
src/backend/model_deployments/azure.py	33.33%	2 Missing ⚠️
src/backend/model_deployments/single_container.py	33.33%	2 Missing ⚠️
src/backend/model_deployments/utils.py	77.77%	2 Missing ⚠️
src/backend/routers/utils.py	0.00%	2 Missing ⚠️
src/backend/config/settings.py	95.45%	1 Missing ⚠️
src/backend/crud/deployment.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #918      +/-   ##
==========================================
+ Coverage   77.23%   77.26%   +0.03%     
==========================================
  Files         281      281              
  Lines       11461    11485      +24     
==========================================
+ Hits         8852     8874      +22     
- Misses       2609     2611       +2     

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[EugeneLightsOn]

Looks great.