feat: Add support for metrics collection

[deelawn]

This PR introduces a package for instrumenting the code for metrics collection. The new README details the environment variables that need to be set and includes an example of how one might configure their local pipeline to export metrics to Grafana Cloud.

I've added a few metrics in the tm2 package; I think they are in the correct spots.

You may notice that the metrics subfolder in the telemetry package is unnecessarily modular. This is because this package originally include code for gathering traces as well. There is an existing issue with this and have decide to presently exclude it from this PR until it is fixed and/or requested -- this is a feature we would almost certainly not want to enable in a production environment. Metrics collection is more likely to be enabled in prod because they can be set to be exported to a local collector application that handles more complex batching, retry requests, and publishing to the end data store, in this case Grafana.

Contributors' checklist...

- [x] Added new tests, or not needed, or not feasible - [x] Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory - [x] Updated the official documentation or not needed - [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message was included in the description - [x] Added references to related issues and PRs - [x] Provided any useful hints for running manual tests - [x] Added new benchmarks to [generated graphs](https://gnoland.github.io/benchmarks), if any. More info [here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).

[zivkovicmilos]

I apologize for being late to the party, I realize this PR has been gathering dust on the shelf for a time now 🙁

Thank you for adding this functionality, it's something I personally see using very frequently. It's also a nice foundation for future (much more robust) metrics in the node 🙏

Pinging @ajnavarro / @gfanton to give a second review. I think this is good to go 🚀

[zivkovicmilos]

Thank you @mazzy89 for the review 🙏

[ajnavarro]

LGTM after resolving all comments 👍

[deelawn]

Finally got this tested and sending metrics to Grafana thanks to @mazzy89 🙇 🙏 🎉

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 47.74%. Comparing base (59c6d3e) to head (4e2edd6).

Files	Patch %	Lines
gno.land/cmd/gnoland/start.go	60.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1762   +/-   ##
=======================================
  Coverage   47.74%   47.74%           
=======================================
  Files         393      393           
  Lines       61637    61647   +10     
=======================================
+ Hits        29430    29436    +6     
- Misses      29736    29738    +2     
- Partials     2471     2473    +2     

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[zivkovicmilos]

@deelawn feel free to merge when you get 1 more approve by @gfanton / @ajnavarro 🙏

[gfanton]

Not much to add after the other reviews. LGTM 👍