Require a colon in //@ normalize-*: test headers

[Zalathar]

The previous parser for //@ normalize-* headers (before #126370) was so lax that it did not require : after the header name. As a result, the test suite contained a mix of with-colon and without-colon normalize headers, both numbering in the hundreds.

This PR updates the without-colon headers to add a colon (matching the style used by other headers), and then updates the parser to make the colon mandatory.

(Because the normalization parser only runs after the header system identifies a normalize header, this will detect and issue an error for relevant headers that lack the colon.)

Addresses one of the points of #126372.

[rustbot]

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[rustbot]

Some changes occurred in src/tools/compiletest

cc @jieyouxu

[Zalathar]

The pattern I used for find/replace was:

• ([ @\]]normalize-[a-z0-9-]*)
• $1: