…-span (#39589)

In an i18n message, two placeholders next to each other must have
an "empty" message-part to separate them. Previously, the source-span
for this message-part was pointing to the wrong original location.
This caused problems in the generated source-maps and lead to extracted
i18n messages from being rendered incorrectly.

PR Close #39589

…n`s (#39589)

The lexer is able to skip leading trivia in the `start` location of tokens.
This makes the source-span more friendly since things like elements
appear to begin at the start of the opening tag, rather than at the
start of any leading whitespace, which could include newlines.

But some tooling requires the full source-span to be available, such
as when tokenizing a text span into an Angular expression.

This commit simply adds the `fullStart` location to the `ParseSourceSpan`
class, and ensures that places where such spans are cloned, this
property flows through too.

PR Close #39589

…9589)

This commit ensures that when leading whitespace is skipped by
the tokenizer, the original start location (before skipping) is captured
in the `fullStart` property of the token's source-span.

PR Close #39589

…er source-spans (#39589)

Tokenized text node may have leading whitespace skipped from their
source-span. But the source-span is used to compute where there are
interpolated blocks, resulting in placeholder nodes whose source-spans
are offset by the amount of skipped characters.

This fix uses the `fullStart` location of text source-spans for computing
the source-span of placeholders, so that they are accurate.

Fixes #39195

PR Close #39589