Read the operational mode from Python components

[shsms]

frequenz-microgrid-component-graph v0.6.1 adds an operational mode to graph
components, but the trait default leaves every component Unspecified — the
bindings have to read the mode off each Python component for it to have any
effect. This builds against v0.6.1, translates the mode, and releases 0.5.1.

Changes

• Bump the crate from v0.6.0 to v0.6.1.
• Translate provides_telemetry() / accepts_control() into one
  OperationalMode in Component::try_new, alongside the existing category
  translation.
• Raise the microgrid extra's floor to frequenz-client-microgrid >= 0.18.4,
  the release the two methods arrived in. On 0.18.3 the mode is never readable
  and the new tests cannot run.
• Write the release notes and bump the version to 0.5.1.

Worth a look

• Both flags or nothing. A mode is named only when both are known:
  provides_telemetry() == false fits Inactive and ControlOnly alike, so a
  half-known mode stays Unspecified rather than being guessed at.
• Missing accessors are tolerated. The assets client has no equivalent
  methods, so their absence reads as unspecified instead of failing the graph —
  the same tolerance the category lookup already has.
• getattr and call0 are separate steps so a missing method reads as
  unspecified while an AttributeError from inside the method body propagates.
  call_method0 cannot tell those apart, and swallowing the second would hide a
  caller's bug and leave the component measuring.