[REQ] A way to access a non-duplicated set of all APIs with multiple tags

[hallami]

Is your feature request related to a problem? Please describe.

Right now, all APIs are bundled by their tags. APIs with multiple tags end up in multiple bundles, meaning duplicates of those APIs.
I'd like a way to access a set (no duplicates) of the APIs.

Describe the solution you'd like

I'd like for there to either be a data section added under/around the apiInfo section that has the APIs not grouped by tags, or for there to be a flag that makes the generator ignore the tags attached to apis.

Describe alternatives you've considered

Going through and stripping out the tags

This means that I'm changing the specification, even if it shouldn't alter any performance.

Manually revising the output

This isn't practical and means that we can't run with the output straight out of the box.

Including tags in the naming schema

This skirts past the name collision issue, but then you still have totally duplicated code with a more confusing name scheme.

Additional context

I've found 3 previous issues that have ran into this same core problem that weren't submitted as requests:
#312
#2844
#8121

[spacether]

I noticed this issue in the python-experimental client and am refactoring the python-experimental generator to generate each endpoint once in this PR: #13007 in the paths module.
When an endpoint has multiple tags, the module for each tag's endpoint imports the existing endpoint which was defined once elsewhere.

One will be able to get apis with:

# get an api by a path (this can act as one api for the entire service)
from package.paths import PathValues
from package.apis.path_to_api import path_to_api
path_enum = PathValues("some/path")
api = path_to_api[path_enum]
# api has .post/put/patch etc methods on it

# get an api by a tag (one endpoint can have multiple tags)
from package.apis.tags import TagValues
from package.apis.tag_to_api import tag_to_api
tag_enum = TagValues("someTag")
api = tag_to_api[tag_enum]
# api has .operation_id etc methods on it

[spacether]

In this PR: #6130
@PhilippParis added the useTags additional property argument.
But it does not appear to suppress multiple tags, it looks like it uses tags for creating interface and controller classnames

[cogwirrel]

For my particular use case, this "normalizer" solved this for me: #14465