When tokenizing markup (e.g. HTML) element attributes
can have quoted or unquoted values (e.g. `a=b` or `a="b"`).
The `ATTR_VALUE` tokens were capturing the quotes, which
was inconsistent and also affected source-mapping.
Now the tokenizer captures additional `ATTR_QUOTE` tokens,
which the HTML related parsers understand and factor into their
token parsing.
PR Close#28055
Removes the tsickle dependency added when tsickle was added to the
transform compiler.
Added a test to ensure stray dependencies are not added and no
errors are introduced during module flattening.
Reworked some of the code so asserts are no longer necessary.
Added additional and potentially redundant checks
Added checks where the null checker found real problems.
PR Close#16422
