feat(self-hosted): convert experimental env vars to config options

[RahulGautamSingh]

Changes

• Converted the following experimental env vars to self-hosted config options

Env var	Config option
RENOVATE_X_DELETE_CONFIG_FILE	deleteConfigFile
RENOVATE_X_EAGER_GLOBAL_EXTENDS	eagerGlobalExtends
RENOVATE_X_IGNORE_NODE_WARN	ignoreNodeWarn
RENOVATE_X_S3_ENDPOINT	s3Endpoint
RENOVATE_X_S3_PATH_STYLE	s3PathStyle

There are some boolean types here. They have not been converted to experimentalFlags because GlobalConfig hasn't been initialized yet, when they are used.

Context

Last of: #27879 (comment)

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository (locally)

[viceice]

this is a problem. We can't set RENOVATE_DELETE_CONFIG_FILE from env, because we don't pass it to the file getConfig. so the config value isn't yet available and causes a breaking change.
also cli flags are not yet available, so wer probably need to move the delete code to a later stage.

@rarkins WDYT?

[rarkins]

@nabeelsaabna can we move this to a later stage and still achieve the goal?

[RahulGautamSingh]

In that case, we could move it to the config/parse/index file, after we have parsed the env vars and cli flags and combined the config.

[RahulGautamSingh]

Verified each migration locally, by either logging the values of each option at runtime or confirming that they are working as expected
check 1: default values passed to functions ☑️
check 2: custom values (from cli, env, file), overwrites default values ☑️
check 3: old env vars parsed and then overwrite the default values ☑️