fix: LEAP-878: Fix shrinking textarea on edit

[hlomzik]

We have TextArea's HtxTextBox (input when you edit text block) updating its height on edit. That was to auto-increase height of multiline blocks. But we stopped taking borders into account some time ago (HumanSignal/label-studio-frontend@c8417d5). Returning it back and fixing condition for empty scrollHeight fixes shrinking input.

• fix position for "Delete Region" icon — it's in the middle now

PR fulfills these requirements

• Tests for the changes have been added/updated
• Docs have been added/updated
• Best efforts were made to ensure docs/code are concise and coherent (checked for spelling/grammatical errors, commented out code, debug logs etc.)
• Self-reviewed and ran all changes on a local instance

Describe the reason for change

Inputs and textareas used to edit TextArea tag text blocks were shrinking every time you type something into them.

This change affects (describe how if yes)

• Performance
• Security
• UX

Does this PR introduce a breaking change?

• Yes, and covered entirely by feature flag(s)
• Yes, and covered partially by feature flag(s)
• No
• Not sure (briefly explain the situation below)

What level of testing was included in the change?

• e2e (codecept)
• integration (cypress)
• unit (jest)

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[hlomzik]

/git merge

Workflow run
Successfully merged: 76 files changed, 772 insertions(+), 1183 deletions(-)

[hlomzik]

/git merge

Workflow run
Successfully merged: 14 files changed, 152 insertions(+), 51 deletions(-)