Many times, in order to create a `ven_pretty::Doc` containing a text
node, the pattern `alloc.text(format!(...))` would be used. This code
then creates a fresh string that is then used in the `Doc`. However,
many times only a small string is necessary and so the allocation could
be optimized. The `ven_pretty` crate supports this through a `SmallString`
type. Allocating a fresh string with `format!` also moves control away
from the `DocAllocator` which isn't ideal, since it could also handle
the string allocations. So, instead of creating a fresh string, one can
simply call `alloc.as_string(format_args!(...))` and delegate the
allocation to the `DocAllocator` without any loss in expressivity. So,
in order to encorage this pattern, this commit also introduces the
`text!` macro.
In order to find all instances of the code pattern, the following
tree-sitter query was used:
```scm
(call_expression
function: (field_expression
field: (field_identifier) @field.name
(#eq? @field.name "text"))
arguments: (arguments
(macro_invocation
macro: (identifier) @macro.name
(#eq? @macro.name "format")))) @reference.call
```
