Add last_evicted field to TxNode

[evanlinjin]

Description

All last_evicted field to TxNode and remove TxGraph::get_last_evicted method.

Notes to the reviewers

get_last_evicted was added as adding fields to TxNode is a breaking change. However, we are going to break bdk_chain in the next release so a breaking change now is okay.

Changelog notice

Added:
- `last_evicted` field is added to `TxNode`.

Removed:
- `TxGraph::get_last_evicted` method is removed.

Checklists

All Submissions:

• I followed the contribution guidelines

New Features:

* [ ] I've added tests for the new feature

• I've added docs for the new feature

[oleonardolima]

ACK 3fb768b

[LagginTimes]

ACK 3fb768b