fix: support quota_project in ErrorReporting client

[torreypayne]

Allows configuring quota_project explicitly in Google::Cloud::ErrorReporting.new and via configuration. This resolves issues where the default quota project from credentials is used but has the Error Reporting API disabled.

closes: #25862

====

manual testing logs:

irb(main):011> Google::Cloud::ErrorReporting.configure { |cfg| cfg.quota_project = 'global-billing-project' }
Key :pretty_print does not exist. Returning nil. at /usr/local/google/home/torreypayne/.gem/ruby/4.0.0/gems/pp-0.6.3/lib/pp.rb:212:in 'block (2 levels) in PP::PPMethods#pp'
=>
irb(main):012> er = Google::Cloud::ErrorReporting.new(project_id: "your-target-project")
=>
#<Google::Cloud::ErrorReporting::Project:0x00007f970b587d80
...
irb(main):013> # Verify it picked up the global configuration
irb(main):014> puts "Service Quota Project: #{er.service.quota_project}"
irb(main):015> puts "GRPC Quota Project: #{er.service.error_reporting.configure.quota_project}"
Service Quota Project: global-billing-project
GRPC Quota Project: global-billing-project
=> nil
irb(main):016> er = Google::Cloud::ErrorReporting.new(project_id: "your-target-project", quota_project: "your-billing-project")
=>
#<Google::Cloud::ErrorReporting::Project:0x00007f97083d6778
...
irb(main):017> # Verify it picked up the global configuration
irb(main):018> puts "Service Quota Project: #{er.service.quota_project}"
irb(main):019> puts "GRPC Quota Project: #{er.service.error_reporting.configure.quota_project}"
Service Quota Project: your-billing-project
GRPC Quota Project: your-billing-project
=> nil
irb(main):020> er = Google::Cloud::ErrorReporting.new(project_id: "your-target-project")
=>
#<Google::Cloud::ErrorReporting::Project:0x00007f9708442018
...
irb(main):021> # Verify it picked up the global configuration
irb(main):022> puts "Service Quota Project: #{er.service.quota_project}"
irb(main):023> puts "GRPC Quota Project: #{er.service.error_reporting.configure.quota_project}"
Service Quota Project: global-billing-project
GRPC Quota Project: global-billing-project