Handle misconfigured clickhouse URL at otel-collector

[ankitnayan]

Currently, if the URL of clickhouse is incorrect, the otel-collectors seg fault with below error

panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x343dd12] goroutine 87 [running]: github.com/SigNoz/signoz-otel-collector/exporter/clickhousemetricsexporter.(*PrwExporter).export.func1() /src/exporter/clickhousemetricsexporter/exporter.go:280 +0xf2 created by github.com/SigNoz/signoz-otel-collector/exporter/clickhousemetricsexporter.(*PrwExporter).export /src/exporter/clickhousemetricsexporter/exporter.go:276 +0x256

All the custom exporters should handle this error and show correct log to help user understand the issue better

[AlexeiZenin]

Slack link for context: https://signoz-community.slack.com/archives/C01HWQ1R0BC/p1665779140680989