fix(proxy-injector): handle proxy-log-level with quotes (#13480)

The proxy accepts log filters in the form `target[fields...]=level`, where a
field may include a value match. This leads to log filters like
`linkerd[name="outbound"]=debug`.

When a log filter is configured via annotation or Helm, the proxy-injector fails
to properly quote the log environment variable, leading to a failure to patch
resources properly.

To fix this, this change ensures that the log level is quoted, which properly
escapes any quotes in the filter itself.

charts/partials/templates/_proxy.tpl

@@ -34,7 +34,7 @@ env:
 - name: LINKERD2_PROXY_SHUTDOWN_ENDPOINT_ENABLED
   value: {{.Values.proxy.enableShutdownEndpoint | quote}}
 - name: LINKERD2_PROXY_LOG
-  value: "{{.Values.proxy.logLevel}}{{ if not (eq .Values.proxy.logHTTPHeaders "insecure") }},[{headers}]=off,[{request}]=off{{ end }}"
+  value: {{ printf "%s%s" .Values.proxy.logLevel (.Values.proxy.logHTTPHeaders | eq "insecure" | ternary "" ",[{headers}]=off,[{request}]=off") | quote }}
 - name: LINKERD2_PROXY_LOG_FORMAT
   value: {{.Values.proxy.logFormat | quote}}
 - name: LINKERD2_PROXY_DESTINATION_SVC_ADDR