fix(topology): consume pending component reloads

[ArunPiduguDD]

Summary

Vector can explicitly reload selected components even when their serialized configuration has not changed. This is used, for example, when a file watched by a component changes.

The selected component names currently remain in the pending reload set after the reload finishes. Consider this sequence:

1. A watched file for component A changes, so Vector explicitly reloads A.
2. Later, an unrelated configuration reload changes only component B.
3. Because A is still in the pending set, Vector unnecessarily restarts both A and B.

Repeated restarts can reset task-local in-memory state and cause unnecessary reconnections, health checks, or brief disruption. This change consumes the pending set when calculating the next topology update. An explicit reload therefore applies once, while a later request can still add the component again.

Vector configuration

Not applicable. This behavior is covered by topology reload tests.

How did you test this PR?

• Added a regression test that verifies a pending component reload is consumed after the next topology reload and can be requested again.
• cargo test pending_component_reloads_are_consumed_after_reload --lib --no-default-features
• make check-clippy
• cargo fmt --all -- --check
• ./scripts/check_changelog_fragments.sh

make check-fmt could not complete because the environment does not have the YAML formatter executable available.

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. A changelog fragment has been added.
• No. A maintainer will apply the no-changelog label to this PR.

References