Remove classic modules (#20)

This commit:

* Removes the ability for users to configure classic module loaders (module.string, module.file, module.git, module.http)
* Removes documentation for the removed components
* Removes documentation referencing "classic modules"

However, the code which enables classic modules has not been removed; this removal will come in a future clean-up effort.

docs/sources/concepts/modules.md

@@ -98,142 +98,6 @@ loki.write "default" {
 }
 ```
 
-{{< collapse title="Classic modules" >}}
-# Classic modules (deprecated)
-
-{{< admonition type="caution" >}}
-Modules were redesigned in v0.40 to simplify concepts.
-This section outlines the design of the original modules prior to v0.40.
-Classic modules are scheduled to be removed in the release after v0.40.
-{{< /admonition >}}
-
-You use _Modules_ to create {{< param "PRODUCT_NAME" >}} configurations that you can load as a component.
-Modules are a great way to parameterize a configuration to create reusable pipelines.
-
-Modules are {{< param "PRODUCT_NAME" >}} configurations which have:
-
-* _Arguments_: Settings that configure a module.
-* _Exports_: Named values that a module exposes to the consumer of the module.
-* _Components_: {{< param "PRODUCT_NAME" >}} components to run when the module is running.
-
-You use a [Module loader][] to load Modules into {{< param "PRODUCT_NAME" >}}.
-
-Refer to [argument block][] and [export block][] to learn how to define arguments and exports for a module.
-
-## Module loaders
-
-A _Module loader_ is a {{< param "PRODUCT_NAME" >}} component that retrieves a module and runs the defined components.
-
-Module loader components are responsible for the following functions:
-
-* Retrieving the module source.
-* Creating a [Component controller][] for the module.
-* Passing arguments to the loaded module.
-* Exposing exports from the loaded module.
-
-Module loaders are typically called `module.LOADER_NAME`.
-
-{{< admonition type="note" >}}
-Some module loaders may not support running modules with arguments or exports.
-{{< /admonition >}}
-
-Refer to [Components][] for more information about the module loader components.
-
-## Module sources
-
-Modules are flexible, and you can retrieve their configuration anywhere, such as:
-
-* The local filesystem.
-* An S3 bucket.
-* An HTTP endpoint.
-
-Each module loader component supports different ways of retrieving `module.sources`.
-The most generic module loader component, `module.string`, can load modules from the export of another {{< param "PRODUCT_NAME" >}} component.
-
-```river
-local.file "my_module" {
-  filename = "PATH_TO_MODULE"
-}
-
-module.string "my_module" {
-  content = local.file.my_module.content
-
-  arguments {
-    MODULE_ARGUMENT_NAME_1 = MODULE_ARGUMENT_VALUE_1
-    MODULE_ARGUMENT_NAME_2 = MODULE_ARGUMENT_VALUE_2
-    // ...
-  }
-}
-```
-
-## Example module
-
-This example module manages a pipeline that filters out debug-level and info-level log lines.
-
-```river
-// argument.write_to is a required argument that specifies where filtered
-// log lines are sent.
-//
-// The value of the argument is retrieved in this file with
-// argument.write_to.value.
-argument "write_to" {
-  optional = false
-}
-
-// loki.process.filter is our component which executes the filtering, passing
-// filtered logs to argument.write_to.value.
-loki.process "filter" {
-  // Drop all debug- and info-level logs.
-  stage.match {
-    selector = "{job!=\"\"} |~ \"level=(debug|info)\""
-    action   = "drop"
-  }
-
-  // Send processed logs to our argument.
-  forward_to = argument.write_to.value
-}
-
-// export.filter_input exports a value to the module consumer.
-export "filter_input" {
-  // Expose the receiver of loki.process so the module consumer can send
-  // logs to our loki.process component.
-  value = loki.process.filter.receiver
-}
-```
-
-You can save the module to a file and then use it as a processing step before writing logs to Loki.
-
-```river
-loki.source.file "self" {
-  targets = LOG_TARGETS
-
-  // Forward collected logs to the input of our filter.
-  forward_to = [module.file.log_filter.exports.filter_input]
-}
-
-module.file "log_filter" {
-  filename = "/path/to/modules/log_filter.river"
-
-  arguments {
-    // Configure the filter to forward filtered logs to loki.write below.
-    write_to = [loki.write.default.receiver],
-  }
-}
-
-loki.write "default" {
-  endpoint {
-    url = "LOKI_URL"
-  }
-}
-```
-
-[Module loader]: #module-loaders
-[argument block]: ../../reference/config-blocks/argument/
-[export block]: ../../reference/config-blocks/export/
-[Component controller]: ../component_controller/
-[Components]: ../../reference/components/
-{{< /collapse >}}
-
 [custom components]: ../custom_components/
 [run]: ../../reference/cli/run/
 [import.file]: ../../reference/config-blocks/import.file/