Various medium-severity bug fixes

[connelly38]

Fixed:

• Make prepared-query byte arrays immutable
• Redact sensitive information from SystemResult.toString() and SystemRequest.toString()
• Add/drop replica retries lack SDK idempotency token support
• Resource-scope header values can inject outbound HTTP headers
• Extension user-agent can inject outbound HTTP headers
• Internal query copies drop caller-specified durability for query DML

[cezarfx]

Both name and value must be checked and there are different rules for them, this is what I got from GPT:

static boolean isValidHttpHeaderName(String name) {
if (name == null || name.isEmpty()) {
return false;
}

for (int i = 0; i < name.length(); i++) {
    char c = name.charAt(i);

    boolean valid =
        (c >= 'A' && c <= 'Z') ||
        (c >= 'a' && c <= 'z') ||
        (c >= '0' && c <= '9') ||
        c == '!' || c == '#' || c == '$' || c == '%' ||
        c == '&' || c == '\'' || c == '*' || c == '+' ||
        c == '-' || c == '.' || c == '^' || c == '_' ||
        c == '`' || c == '|' || c == '~';

    if (!valid) {
        return false;
    }
}

return true;

}

static boolean isValidHttpHeaderValue(String value) {
if (value == null) {
return false;
}

for (int i = 0; i < value.length(); i++) {
    char c = value.charAt(i);

    // Reject control chars except horizontal tab.
    // This rejects CR/LF too, preventing header injection.
    if ((c < 0x20 && c != '\t') || c == 0x7f) {
        return false;
    }
}

return true;

}

Also http2 and 3 should also check:
if (c >= 'A' && c <= 'Z') {
return false;
}

[connelly38]

We don't have a way for users to affect the header field that we send. We only allow appending to the value. So I don't think we need header field validation at this point.
The purpose of this change was to eliminate the chance of injected headers, so throwing an error on CR/LF is really the most important part. The current code change covers that with the simple <= 0x1f check.