Lazy execute recorded as block

[Gabriel-Darbord]

Similar to #47
Add lazy behavior to TinyLogger>>#execute:recordedAs: such that:

• If no loggers are set, then the execute block runs immediately.
• The second argument can be a block that will only be evaluated if necessary.

In addition:

• Rename arg aString to aBlockOrString where applicable.
• Add space before error message when execute:recordedAs: is interrupted.
• Remove use of value:during: in TinyLoggerTest, since it is now done in performTest.
• Add a test for value:during: to check that the previous logger is restored.

[jecisc]

Thank!