perf(router): use resty.core.utils.str_replace_char() for dashes

[chronolaw]

Summary

resty.core.utils.str_replace_char() is a better way to replace - to _.
In the future string.lua will gather more functions to simplify tools.utils.lua.

See: #10443

Checklist

• The Pull Request has tests
• A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Full changelog

• [Implement ...]

Issue reference

Fix #[issue number]

[chobits]

hi @chronolaw

It seems there are some other files needed to be fixed. see the following matched files:

 $ grep '"-".*"_"' -R kong|grep gsub|grep -v cscope.out
kong/runloop/plugin_servers/process.lua:      local env_prefix = "pluginserver_" .. name:gsub("-", "_")
kong/plugins/datadog/handler.lua:    return consumer and gsub(consumer.id, "-", "_")
kong/clustering/compat/init.lua:      local name = gsub(t["name"], "-", "_")
kong/clustering/compat/checkers.lua:            local new_prefix = prefix:gsub("-", "_")
kong/vaults/env/init.lua:  resource = upper(gsub(resource, "-", "_"))
kong/pdk/vault.lua:        local env_name = gsub(name, "-", "_")
kong/pdk/vault.lua:          local n = lower(fmt("vault_%s_%s", env_name, gsub(k, "-", "_")))
kong/pdk/service/response.lua:        local var = fmt("upstream_http_%s", gsub(lower(name), "-", "_"))
kong/pdk/service/response.lua:      name = gsub(name, "-", "_")
kong/pdk/service/response.lua:        n = gsub(lower(n), "-", "_")
kong/router/atc.lua:      local name = name:gsub("-", "_"):lower()
kong/router/compat.lua:        local name = "any(http.headers." .. h:gsub("-", "_"):lower() .. ")"

[chronolaw]

Yes, replace_dashes is a very common operation, but I don't want to change too many source, which is hard to review.

This PR focus on router scope only, after this PR is merged, we can optimize other soucres.