feat: add event bus and triggers

[radu-mocanu]

This PR aims to extract the common entities from uipath-platform and other libraries to further decouple the SDK.

Extracted:

• event bus from https://github.com/UiPath/uipath-python (ref: chore: import triggers from core uipath-runtime-python#95)
• serialize_object helper and trigger models from https://github.com/UiPath/uipath-runtime-python (ref: feat: extract platform module to uipath-platform library uipath-python#1354)

Development Package

• Use uipath pack --nolock to get the latest dev build from this PR (requires version range).
• Add this package as a dependency in your pyproject.toml:

[project]
dependencies = [
  # Exact version:
  "uipath-core==0.5.2.dev1000450227",

  # Any version from PR
  "uipath-core>=0.5.2.dev1000450000,<0.5.2.dev1000460000"
]

[[tool.uv.index]]
name = "testpypi"
url = "https://test.pypi.org/simple/"
publish-url = "https://test.pypi.org/legacy/"
explicit = true

[tool.uv.sources]
uipath-core = { index = "testpypi" }

[tool.uv]
override-dependencies = [
    "uipath-core>=0.5.2.dev1000450000,<0.5.2.dev1000460000",
]