Clarify exception catching language

[domenic]

Closes #2842, by explicitly using the word "catch" when catching
exceptions. This also aligns better with Infra's conventions.

This also cleans up a number of instances where we explicitly propagate
exceptions, which per Infra is not necessary; instead we simply note
parenthetically that the operations in question can throw.

/cc @EdgarChen @bzbarsky @annevk

[annevk]

We should maybe level some of this language up to Infra?

[domenic]

It kind of is already:

"Throw" will make the caller automatically rethrow the given value, if any, and thereby terminate the caller’s algorithm. Using prose the caller has the ability to "catch" the exception and perform another action.

[bzbarsky]

The proposed changes look pretty good to me at first glance. Thank you!