feat: get schema by schema_type

[Jaycean]

What this PR does / why we need it:

• part fix plugin(hmac-auth): update the schema #2441

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible?

[Jaycean]

@membphis PTAL,Thx

[Jaycean]

@membphis I have some questions to discuss with you.

The method I currently implement is to directly determine whether to return consumer_schema through whether the query field has schema_type=consumer in apisix/admin/plugins.lua.

    local arg = get_uri_args()
    local json_schema = plugin.schema
    if arg and arg["schema_type"] == "consumer" then
        json_schema = plugin.consumer_schema
    end

#2441 (comment)
I thought of another implementation method to obtain the corresponding schema directly through the value of schema_type, but if Obtain directly through the value of schema_type, then you need to pass the corresponding complete schema_type:/apisix/admin/schema/plugins/{plugin_name}?schema_type=consumer_schema
Instead of: /apisix/admin/schema/plugins/{plugin_name}?schema_type=consumer

[membphis]

/apisix/admin/schema/plugins/{plugin_name}?schema_type=consumer

I think this way is simpler and enough.

[juzhiyuan]

LGTM

[liuxiran]

LGTM

tips:
after this pr merged, jwt-auth also needs to add consumer_schema to the _M @Jaycean

apisix/apisix/plugins/jwt-auth.lua

Line 59 in 1dfc4cd

local _M = {

[Jaycean]

LGTM

tips:
after this pr merged, jwt-auth also needs to add consumer_schema to the _M @Jaycean

apisix/apisix/plugins/jwt-auth.lua

Line 59 in 1dfc4cd

local _M = {

OK, I will submit a new PR unified addition to consumer_schema support

[juzhiyuan]

LGTM

tips:
after this pr merged, jwt-auth also needs to add consumer_schema to the _M @Jaycean

apisix/apisix/plugins/jwt-auth.lua

Line 59 in 1dfc4cd

local _M = {

• TODO this issue