Add ability to configure sampling rate based on transaction span name

[jclusso]

What does this pull request do?

Adds new configuration option so you can set the sampling rate by transaction name. I'm not 100% certain this is the correct way to do this, so please let me know if I should be going about this in a different manner.

{
  transaction_sample_rate_by_name: {
    "UsersController#index": 1.0
    "HealthController#ping": 0
  }
}

Why is it important?

When you have an application with certain portions that get a significant amount of traffic, there is currently no good way to control the sampling. Either you are blind to low volume transactions or have to collect a lot more samples than you need. You can currently get around this with Tail-based sampling, but this is not available on serverless. This also still requires you send a ton of data to your APM server that you may not need to.

Checklist

• I have signed the Contributor License Agreement.
• My code follows the style guidelines of this project (See .rubocop.yml)
• I have rebased my changes on top of the latest main branch
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have made corresponding changes to the documentation
• I have updated docs/release-notes/index.md
• I have updated docs/reference/supported-technologies.md
• Added an API method or config option? Document in which version this will be introduced

Related issues

Resolves #1334