Implement tree explain for FilterExec

[alamb]

Which issue does this PR close?

• Closes Implement tree explain for FilterExec #15000
• Part of [EPIC] Complete SQL EXPLAIN Tree Rendering #14914

Rationale for this change

Let's have nice explain plans!

I wanted an example of how to make a tree explain plan so that I can file a bunch of follow on tickets for #14914 to share the work

What changes are included in this PR?

1. Update comments about ExplainFormat
2. Implement for FilterExec
3. Update tests

Are these changes tested?

Yes

Are there any user-facing changes?

tree explain is better

[irenjj]

This is a very nice case for // TODO: check every line is less than MAX_LINE_RENDER_SIZE. In DuckDB, we can get the following result:

D explain select * from t1 where c != 'foo' and c != 'bar' and c != 'a really long string constant';

┌─────────────────────────────┐
│┌───────────────────────────┐│
││       Physical Plan       ││
│└───────────────────────────┘│
└─────────────────────────────┘
┌───────────────────────────┐
│         SEQ_SCAN          │
│    ────────────────────   │
│         Table: t1         │
│   Type: Sequential Scan   │
│       Projections: c      │
│                           │
│          Filters:         │
│ c!='foo' AND c!='bar' AND │
│  c!='a really long string │
│          constant'        │
│                           │
│          ~1 Rows          │
└───────────────────────────┘

[irenjj]

I will try to make it the same as DuckDB later.

[alamb]

Awesome -- thank you. Maybe we can file a ticket to track the idea?