age: Replace callback input read_line_initial_text with write_str and read_line

[thibmeu]

read_line_initial_text fills the tty input with the initial text. This implies that the returned input is usually prefixed with the initial text, or that the initial text can be removed.
This differs from age behaviour, which is to not allow the initial text to be removed.

As a consequence, plugin leveraging callbacks for reading public input (confirm, request_public_string) exhibit a different behaviour depending on if they are called with age or rage.

This commit replaces read_line_initial_text with write_str and read_line. The initial text is still displayed to the user, but it does not affect the returned output.

[str4d]

This is not at all how I thought console::Term::read_line_initial_text worked; I thought the initial text was a description being displayed in front of the text input, not forming part of the response. Good catch, thanks!

[codecov]

Codecov Report

Merging #406 (634e567) into main (ea42d81) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #406      +/-   ##
==========================================
- Coverage   40.88%   40.87%   -0.02%     
==========================================
  Files          34       34              
  Lines        3248     3249       +1     
==========================================
  Hits         1328     1328              
- Misses       1920     1921       +1     

Files Changed	Coverage Δ
age/src/cli_common.rs	13.68% <0.00%> (-0.15%)	⬇️

... and 2 files with indirect coverage changes

[str4d]

utACK, thanks!