Add missing colors to erc-irccontrols-mode

Add missing colors to erc-irccontrols-mode

* lisp/erc/erc-goodies.el (erc-spoiler-face): Add new face.
(erc--controls-additional-colors): Add remaining 16-99 colors.
(erc-get-bg-color-face, erc-get-fg-color-face): Look up extended
colors in table.
(erc-controls-remove-regexp, erc-controls-highlight-regexp): Convert
to `rx' forms and move above first use to eliminate intra-file forward
declarations.
(erc-controls-propertize): Support spoilers.
* test/lisp/erc/erc-goodies-tests.el: New file.  (Bug#60954.)