[GEN-1947]: add Better Stack destination support and documentation

[BenElferink]

This pull request introduces the integration of Better Stack as a new destination for observability data in Odigos, along with various documentation updates and improvements. The most important changes include the addition of Better Stack configuration, updates to the README.md and documentation files, and modifications to the configuration files to support Better Stack.

Better Stack Integration:

• common/config/betterstack.go: Added new configuration for Better Stack, including methods to modify the configuration and set up exporters and pipelines.
• common/config/root.go: Included BetterStack in the list of available configers.
• common/dests.go: Added BetterStackDestinationType to the list of destination types.
• destinations/data/betterstack.yaml: Created a new YAML file for Better Stack destination configuration, specifying supported signals and required fields.

Documentation Updates:

• docs/backends/betterstack.mdx: Added a new documentation page for configuring Better Stack as a backend in Odigos.
• docs/backends-overview.mdx: Updated the overview to include Better Stack as a managed destination.
• docs/mint.json: Updated the documentation structure to include Better Stack and reformatted several sections for consistency. [1] [2] [3] [4] [5] [6] [7]
• docs/quickstart/next-steps.mdx: Added Better Stack to the list of backends in the quickstart guide.

README Updates:

• README.md: Minor formatting changes to the key features section and updated the list of managed destinations to include Better Stack. [1] [2] [3]

[notion-workspace]

Destinations: add support for “Better Stack”