apacheGH-17682: [Format] Add Bool8 Canonical Extension Type (apache#4…

…3234)

### Rationale for this change

Closes: apache#17682

Arrow Boolean arrays store values as individual bits, which is a very compact representation but does not match the layout of many systems with which it interoperates. By adding an 8-bit Boolean extension type, zero-copy compatibility with many systems can be improved at the cost of large physical representation.

Go implementation: apache#43323
C++ / Python implementation: apache#43488

### What changes are included in this PR?

Proposal and documentation for `Bool8` canonical extension type.

### Are these changes tested?

N/A

### Are there any user-facing changes?

N/A

* GitHub Issue: apache#17682

Lead-authored-by: Joel Lubinitsky <[email protected]>
Co-authored-by: Joel Lubinitsky <[email protected]>
Co-authored-by: Felipe Oliveira Carvalho <[email protected]>
Signed-off-by: Joel Lubinitsky <[email protected]>

docs/source/format/CanonicalExtensions.rst

@@ -393,6 +393,28 @@ Examples:
 
     {"type_name": "OTHER", "vendor_name": "JDBC driver name"}
 
+8-bit Boolean
+=============
+
+Bool8 represents a boolean value using 1 byte (8 bits) to store each value instead of only 1 bit as in
+the original Arrow Boolean type. Although less compact than the original representation, Bool8 may have
+better zero-copy compatibility with various systems that also store booleans using 1 byte.
+
+* Extension name: ``arrow.bool8``.
+
+* The storage type of this extension is ``Int8`` where:
+
+  * **false** is denoted by the value ``0``.
+  * **true** can be specified using any non-zero value. Preferably ``1``.
+
+* Extension type parameters:
+
+  This type does not have any parameters.
+
+* Description of the serialization:
+
+  Metadata is an empty string.
+
 =========================
 Community Extension Types
 =========================